- Centre of Excellence in Solid State Physics,
University of the Punjab, QAC
Lahore-54590, PAKISTAN - +92-42909231135
- Physics, Microelectronics And Semiconductor Engineering, Spintronics, Nanotechnology, Nanoscience, Education, and 17 morePhotovoltaics, Thin Films and Coatings, Optoelectronics, Superconductivity, Thin Films, Laser Ablation, Electronic Devices, Semiconductor thin films, Optical Coatings, Magnetic Materials, Materials Science, Solar Energy, Nanomaterials, Titania Nanotubes, Sol-gel Synthesis, Magnetism and Magnetic Materials, and Biomedical Sciencesedit
- Dr. Shahzad Naseem is Professor of Solid State Physics at University of the Punjab. He has published / presented more... moreDr. Shahzad Naseem is Professor of Solid State Physics at University of the Punjab. He has published / presented more than 1000 papers with a cumulative impact factor of around 500. He has supervised more than 200 research theses in the important fields of Optical Coatings, Photovoltaics, Ferroelectric Liquid Crystals and Spintronic Devices. Dr. Shahzad has setup various research labs and has introduced MS Microelectronics and MS Nanotechnology degrees in Pakistan. In his career, Prof. Shahzad Naseem was awarded a Gold Medal in his MSc and has won a prestigious Post-Doctoral Award of Association of Commonwealth Universities. He has also been awarded a Gold Medal in Physics by the Pakistan Academy of Sciences.edit
ABSTRACT A simple tunable laser structure with quasi-continuous tuning range of 15 nm, more than 30 dB side mode suppression ratio, 400 kHz linewidth and low variation in output power over the tuning range is demonstrated. The device... more
ABSTRACT A simple tunable laser structure with quasi-continuous tuning range of 15 nm, more than 30 dB side mode suppression ratio, 400 kHz linewidth and low variation in output power over the tuning range is demonstrated. The device involved minor modifications to a standard Fabry Perot (FP) laser and measurements have confirmed modeled predictions. Prototype fabrication has used focussed ion beam etching to generate three reflection/scattering sites with power reflectivity of approximately 1%, at precise locations along the optical axis of a 1500 nm FP laser. The device contact was electrically split at these reflection/scattering sites, thereby generating weak FP cavities within a strong primary FP cavity. Tuning is achieved by precisely changing the currents to each section and hence altering the refractive indices.
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Abstract Flurbiprofen loaded PCL/PVP blend micro-spheres were prepared by o/w solvent evaporation method using various concentrations of gelatin as emulsifying agent. Microsphere recovery decreased with a decrease in the concentration of... more
Abstract Flurbiprofen loaded PCL/PVP blend micro-spheres were prepared by o/w solvent evaporation method using various concentrations of gelatin as emulsifying agent. Microsphere recovery decreased with a decrease in the concentration of the emulsifier in the dispersion. Encapsulation ...
Research Interests: Materials Engineering, Materials Science, Pharmacy, Electron Microscopy, Kinetics, and 15 moreEvaporation, Dispersion, Models, Ph, Recovery, FORMULATION, Crystallinity, Efficiency, Encapsulation, Powder, Fourier transform infrared spectroscopy, Microsphere, Microspheres, Infrared Spectrometry, and Drug Release
Multiferroic materials are of particular interest due to the co-existence of ferromagnetic and ferroelectric properties. Among various multiferroics, bismuth iron oxide (BiFeO3, BFO) is the only material that shows both ferroelectric and... more
Multiferroic materials are of particular interest due to the co-existence of ferromagnetic and ferroelectric properties. Among various multiferroics, bismuth iron oxide (BiFeO3, BFO) is the only material that shows both ferroelectric and antiferromagnetic properties at room temperature. However, synthesis of phase pure BFO is difficult due to volatile nature of Bi2O3. In this work, bismuth iron oxide nanoparticles are synthesized using sol-gel technique. With change in synthesis conditions a transition from amorphous nature to crystalline behavior is observed. The crystalline nature of nanoparticles strongly affects the dielectric and magnetic properties. High dielectric constant of ~300 (frequency =1kHz) is obtained due to presence of less conducting grain boundaries. Ferromagnetic behavior, instead of antiferromagnetic bismuth iron oxide, arises due to suppression of spiral spin structure of bismuth iron oxide.
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Multiferroic materials are of particular interest due to the co-existence of ferromagnetic and ferroelectric properties. Among various multiferroics, bismuth iron oxide (BiFeO3, BFO) is the only material that shows both ferroelectric and... more
Multiferroic materials are of particular interest due to the co-existence of ferromagnetic and ferroelectric properties. Among various multiferroics, bismuth iron oxide (BiFeO3, BFO) is the only material that shows both ferroelectric and antiferromagnetic properties at room temperature. However, synthesis of phase pure BFO is difficult due to volatile nature of Bi2O3. In this work, bismuth iron oxide nanoparticles are synthesized using sol-gel technique. With change in synthesis conditions a transition from amorphous nature to crystalline behavior is observed. The crystalline nature of nanoparticles strongly affects the dielectric and magnetic properties. High dielectric constant of ~300 (frequency =1kHz) is obtained due to presence of less conducting grain boundaries. Ferromagnetic behavior, instead of antiferromagnetic bismuth iron oxide, arises due to suppression of spiral spin structure of bismuth iron oxide.
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Multiferroic materials like Bismuth Iron Oxide (BiFeO3), YMnO3, BiMnO3, TbMnO3 has attracted worldwide attraction due their applications in data storage devices, spintronic devices, sensors and multiple stage memories. Among these... more
Multiferroic materials like Bismuth Iron Oxide (BiFeO3), YMnO3, BiMnO3, TbMnO3 has attracted worldwide attraction due their applications in data storage devices, spintronic devices, sensors and multiple stage memories. Among these materials BiFeO3 is a promising candidate as it exhibits room temperature antiferromagnetic and ferroelectric properties. However, BiFeO3 suffers from some drawbacks including weak magnetic behavior, inhomogeneity in spin structure and large leakage current. In order to overcome these problems we here report Lanthanum (La) doped Bi1-xLaxFeO3 (where, x=0.0-0.5) thin films prepared by sol-gel method. The effect of La substitution on structural and dielectric properties has been investigated. The films show pure phase rhombohedrally distorted perovskite structure of BiFeO3. XRD peak shifts to high angles due to slight difference in ionic radii of La (1.16Å) and Bi (1.17Å). The dielectric constant and tangent loss decreases as frequency increases and becomes c...
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ZnO semiconductor is a potential candidate for the information processing, energy storage, communication and optoelectronic devices. Various physical properties of the ZnO have been demonstrated both experimentally and theoretically. We... more
ZnO semiconductor is a potential candidate for the information processing, energy storage, communication and optoelectronic devices. Various physical properties of the ZnO have been demonstrated both experimentally and theoretically. We reported the different characteristics of undoped and Indium doped ZnO using first principle calculations under the framework of density functional theory. Both wurtzite and zincblende phases of the ZnO are examined using local density approximations (LDA) and generalized gradient approximation (GGA) with different exchange correlation potential within DFT for band structure calculations. Results reveal that the pure ZnO is a direct band gap semiconductor which can be employed for wide range of optoelectronics devices. The accuracy of the results are also checked with reported experimental data which are in consistent. We investigated Indium metal doped ZnO, in order to explore the influence of the doping on structural and optical properties. The ban...
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Iron Oxide has gained much interest in biomedical and spintronics applications due to its unique and novel properties. Amsterdam density functional (ADF) software is used for the first time in order to theoretically investigate the... more
Iron Oxide has gained much interest in biomedical and spintronics applications due to its unique and novel properties. Amsterdam density functional (ADF) software is used for the first time in order to theoretically investigate the structural properties of cobalt doped iron oxide at 0K. TZ2P is used as basis set. Using GGA geometry optimization was achieved to observe structural properties. Inverse spinel cubic structure with lattice parameter of 8.39 Å is confirmed after geometry optimization by using GGA. 2X1X1 super cell of cobalt doped iron oxide is formed and GGA:PBE method is used to obtain total density of states (DOS) along with partial DOS of iron, cobalt and oxygen, respectively. Increase in band gap energy at 0K is observed after applying Hubbard potential (U=3 and 4 eV) for cobalt and iron, respectively.
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The un-doped and Fe-doped ZnS nanocrystalline thin films were deposited on glass substrates by chemical bath deposition (CBD). Iron chloride, zinc chloride and thioacetamide were used as precursors and de-ionized water was used as... more
The un-doped and Fe-doped ZnS nanocrystalline thin films were deposited on glass substrates by chemical bath deposition (CBD). Iron chloride, zinc chloride and thioacetamide were used as precursors and de-ionized water was used as solvent. The synthesis and deposition of thin films was carried out without using any surfactant/capping agent. The powder X-ray diffraction patterns reveal the formation of cubic zinc blende phase of ZnS in all cases. The incorporation of iron in ZnS lattice was confirmed by the change in lattice parameters accordingly with doping concentration and absence of traces of secondary phases or Fe clusters. The M-H curves indicate that doped ZnS thin films exhibit room temperature ferromagnetism. The magnetization properties as a function of field angle and doping concentration were studied in detail. The density functional calculations were performed using Full Potential Linearized Augmented Plane Wave (FPLAPW) as is employed in elk-code. The strong p-d hybrid...
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Magnetic nanostructures including nanowires (NWs) and nanotubes (NTs) have attracted considerable scientific interest during the last decade because of their potential applications in sensors, microwave absorption, biological separation... more
Magnetic nanostructures including nanowires (NWs) and nanotubes (NTs) have attracted considerable scientific interest during the last decade because of their potential applications in sensors, microwave absorption, biological separation and high density recording media. A comprehensive study of magnetization properties for MCoO (M=Ni, Fe) core-shell nanowires has been carried out. Ferromagnetic nanowires arrays layered with Cobalt oxide shell are fabricated by sol gel route followed by DC electrodeposition into AAO templates. Scanning electron microscope was used to analyse the morphology of fabricated nanowires. Structural analyses reveal the formation of highly ordered, dense and uniformly distributed core-shell nanowires. Magnetic hysteresis loops indicated that for core-shell nanowires easy axis of magnetization lie parallel to the wire long axis.
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Tin oxide (SnO2) doped and un-doped indium oxide (In2O3) nanoparticles are synthesized by the sol-gel method while anhydrous indium chloride (InCl3) and anhydrous tin chloride (SnCl4) are used as the source of indium and tin respectively,... more
Tin oxide (SnO2) doped and un-doped indium oxide (In2O3) nanoparticles are synthesized by the sol-gel method while anhydrous indium chloride (InCl3) and anhydrous tin chloride (SnCl4) are used as the source of indium and tin respectively, for the formation of indium tin oxide (ITO) thin films. Ethanol is used as solvent to get homogenous solution. Acetic acid (CH3COOH) was also added drop wise in this solution. Thin films of doped and un-doped In2O3 are deposited on glass substrate at room temperature and annealed at different temperatures ranging from 50°C to 500°C. The XRD patterns of thin films indicates the main peak of (12 4 ) plane and showed a higher degree of crystallinity in annealed thin films. Average crystallite size of 10.9 nm to 29.3 nm is observed in all the deposited thin films. The optical transmittance spectra of SnO2 doped In2O3 thin films showed the fundamental absorption edge with increment in annealing temperature. The band gap of thin films is observed to be f...
Gold nanoparticles, owing to their fascinating optical properties, are considered very attractive for detecting devices. Size, shape as well as surrounding environment may affect the sensing behavior of nanomaterial and thus the study of... more
Gold nanoparticles, owing to their fascinating optical properties, are considered very attractive for detecting devices. Size, shape as well as surrounding environment may affect the sensing behavior of nanomaterial and thus the study of such factors is of great importance. We investigatedthe gas sensing performance of colloidal gold nanoparticles of different sizes in carbon dioxide gaseous environment by measuring the optical behavior with and without gas. The citrate reduction method was adopted to synthesize gold nanoparticles; scanning electron microscopy was used for morphological studies while optical properties were determined by spectroscopic ellipsometery. We observed a size dependent decrease in the transmission spectra of colloidal gold nanoparticles in the presence gaseous environment.
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ABSTRACT Doping effects of acidic (pH4) and basic (pH10) Fe3O4 on the magnetic properties of ZrO2 have been reported in this paper. Fe3O4 doped zirconia (FZ) sol is synthesized by varying Fe3O4 concentrations in the range of 2–10 wt%... more
ABSTRACT Doping effects of acidic (pH4) and basic (pH10) Fe3O4 on the magnetic properties of ZrO2 have been reported in this paper. Fe3O4 doped zirconia (FZ) sol is synthesized by varying Fe3O4 concentrations in the range of 2–10 wt% using sol-gel route. FZ sols are spin coated onto glass substrates and then vacuum annealed at 300 °C for 60 min in the presence of 500 Oe magnetic field. X-ray diffraction results show amorphous behavior at 2 wt% doping in both acidic and basic cases. Mixed monoclinic-tetragonal behavior is observed in acidic films with 6–10 wt% doping concentration. However, tetragonal phase is observed in basic films with 8–10 wt% doping. Soft ferromagnetic behavior is observed in both the acidic and basic doped zirconia. Saturation magnetization (M (_{mathrm {s}}) ) of (sim 33) emu/g is observed in acidic FZ samples whereas, variation in M (_{mathrm {s}}) (1–36 emu/g) is observed in basic FZ samples. Iron oxide stabilized ZrO2, with soft ferromagnetic behavior, can be employed for coatings on teeth as well as for diagnosis and therapy of oral cancer.
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ABSTRACT The safe, targeted and effective release of drugs for therapeutics from nanostructured functional materials, particularly nanoparticles (NPs), has attracted much attention due to the ability to diagnose and cure of cancer and... more
ABSTRACT The safe, targeted and effective release of drugs for therapeutics from nanostructured functional materials, particularly nanoparticles (NPs), has attracted much attention due to the ability to diagnose and cure of cancer and other ailments. The potential of magnetic NPs, that stems from intrinsic properties of their magnetic cores combined with their drug, can be exploited for clinical applications. Two main magnetic requirements for bionanotechnology—a high saturation magnetic moment and a near-zero remanence—occur in superparamagnetic materials. Here, we report synthesis of magnetite NPs by modified coprecipitation method. The effect of pH on the shape and size of NPs has also been reported in this paper. For superparamagnetic nature, the size of the NPs has great significance and should be compatible with the living cell. Ferric and ferrous chlorides are used as precursors and the amount of NaOH was varied to control the size and shape of the nanoparticles. X-ray diffraction patterns show the formation of magnetites. Scanning electron microscopy reveals that the prepared nanoparticles have size compatible with the diseased cell. M-H curves show the superparamagnetic nature of the nanoparticles, hence these NPs are well suited for the magnetic resonance imaging as the contrast agents, for cell tagging, magnetic separation, and hyperthermia treatments.
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ABSTRACT Mn/Fe co-doped ZnO thin films are prepared by simple sol–gel and spin coating method. Five different sols with the change in concentration (1–5 wt%) of both Mn and Fe are synthesized. Molar ratio of Mn and Fe is kept constant,... more
ABSTRACT Mn/Fe co-doped ZnO thin films are prepared by simple sol–gel and spin coating method. Five different sols with the change in concentration (1–5 wt%) of both Mn and Fe are synthesized. Molar ratio of Mn and Fe is kept constant, i.e., 1:1. Sols are spun onto glass and copper substrates by spin coating method followed by the post magnetic field annealing at 300 °C for 1 h. Effect of Mn and Fe codoping on ferromagnetic properties of ZnO is reported in this paper. Structural and magnetic properties of as prepared and annealed samples are investigated by X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM). Scanning electron microscope is used to study the surface morphology of co-doped films. XRD results show incorporation of Mn and Fe in the host lattice upto a dopant concentration of 4 wt%. However, small crystallites of Mn and Fe2O3 are observed by increasing the dopant concentration to 5 wt%. VSM results indicate room temperature ferromagnetism in all samples without the presence of any secondary phases. Low value of shape anisotropy is observed in the case of Mn doped ZnO. However, no shape anisotropy is observed in the case of co-doped thin films. Moreover, Mn/Fe co-doped thin films show magnetic hysteresis equivalent to that of multilayered structure, indicating that such complex structures used in spintronic devices can be replaced by a single ZnO layer with codoping of Mn and Fe.
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Impact ionization in fully depleted (FD) Silicon On Insulator (SOI) n-Channel MOSFET is investigated as a function of the doping concentration. We have found that impact ionization increases with the decrease in the doping concentration... more
Impact ionization in fully depleted (FD) Silicon On Insulator (SOI) n-Channel MOSFET is investigated as a function of the doping concentration. We have found that impact ionization increases with the decrease in the doping concentration and vice versa. Simulation results obtained from Sentaurus TCAD with the higher doping concentration can control the threshold voltage (V th). Furthermore we have examined the effect of doping concentration on the transconductance (g m) and have observed that transconductance is inversely proportional of the doping concentration.
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Magnetic nanoparticles have attracted broad attention due to their potential biomedical applications, such as contrast agents for magnetic resonance imaging (MRI), heating mediators for cancer therapy (hyperthermia), and magnetic labels... more
Magnetic nanoparticles have attracted broad attention due to their potential biomedical applications, such as contrast agents for magnetic resonance imaging (MRI), heating mediators for cancer therapy (hyperthermia), and magnetic labels for biosensing. For nanoparticles to be utilized for biomedical applications these nanoparticles must acquire superparamagnetic behavior with relatively high value of saturation magnetization [1-3]. However, the main challenge in the use of these nanoparticles is the functionalization of particle surface [4-5]. Magnetite (Fe3O4) nanoparticles, with diameter of ~20nm, are synthesized using sol-gel method. Uncoated Fe3O4 nanoparticles show superparamagnetic behavior as shown in Fig. 1. For making these nanoparticles useful in MRI contrast agent, nanoparticles were coated with citric acid. Citric acid (C6H8O7) is a short chained molecule containing three carboxylate groups [6-8]. Citric acid gets adsorbed on the surface of superparamagnetic iron oxide n...
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Wear and friction behaviour of yttria stabilised zirconia coatings are very sensitive to the structure of the material and test parameters such as temperature, applied load, sliding speed, and environment. The present study describes the... more
Wear and friction behaviour of yttria stabilised zirconia coatings are very sensitive to the structure of the material and test parameters such as temperature, applied load, sliding speed, and environment. The present study describes the friction, and sliding wear behaviours of plasma sprayed yttria stabilized zirconia coating (ZrO 2 -8wt.%Y 2 O 3 (YSZ) deposited on a stainless steel substrate with NiAl bond coat. Tribological properties of the coating were assessed under lubrication condition at loads of 4N and 8N. The frictional behaviour of coating was assessed at a constant temperature of 50°C, while wear characteristics of the coating were investigated at 50°C and 100°C. The experimental results of this study showed a slight decrease in frictional coefficient with increasing load. However, the coating wear rate was slightly increased with increasing load and temperature. The coating wear mainly involved materials transferred from the counter body and pulling-out from the coatin...
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Present work is an appraisal of the effectiveness of FeO in the stabilization of tetragonal zirconia (ZrO2) nanoparticles synthesized under different conditions for biomedical especially dental applications. Zirconia based ceramics have... more
Present work is an appraisal of the effectiveness of FeO in the stabilization of tetragonal zirconia (ZrO2) nanoparticles synthesized under different conditions for biomedical especially dental applications. Zirconia based ceramics have found broad biomedical applications because of their unusual combination of strength, fracture toughness, hardness, and low thermal conductivity. These attractive characteristics are largely associated with the stabilization of tetragonal and cubic phases through alloying with aliovalent ions. The high fracture toughness exhibited by many of zirconia ceramics is attributed to the tetragonal to monoclinic phase transformation and its release during crack propagation. Objectives of the present work include preparation of α-Fe2O3 doped and un-doped ZrO2 nano-powders by sol-gel method. This work also includes thin film growth of zirconia nanoparticles with a thickness of 100 nm by spinning the sol onto glass substrates. Temperature, pH, nature of solvent...
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3with average value of 787.5 µg/m 3 for Faisalabad respectively. Most of these values are normal and as reported in the literature for other parts of the world. The major phases identified in the samples by the x-ray powder diffraction... more
3with average value of 787.5 µg/m 3 for Faisalabad respectively. Most of these values are normal and as reported in the literature for other parts of the world. The major phases identified in the samples by the x-ray powder diffraction technique are albite (anorthite), calcite, clinochlore (chlorite), gypsum, illite, quartz and talc which have also been reported by other researchers to be present in the solid aerosols of other world locations. The average weight percentages of the phases in the samples are respectively 47.88, 22.04, 24.55, 11.02, 21.75 and 9.12 for Faisalabad.
Structural and hence the electrical properties of transition metal doped ZnO-based dilute magnetic semiconductors can effectively be tuned thermally for their potential utilization in high temperature modern day spintronic devices. In... more
Structural and hence the electrical properties of transition metal doped ZnO-based dilute magnetic semiconductors can effectively be tuned thermally for their potential utilization in high temperature modern day spintronic devices. In this work, we investigate the effect of Mn doping on structural and its consequent effects on the electrical characteristics of Zn0.95−xMnxFe0.05O (x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05) synthesized using sol–gel auto-combustion. X-ray diffraction analysis indicated that the synthesized samples had the pure wurtzite-type hexagonal crystal structure. Average crystallite size as determined using Scherrer’s formula was decreased with the increase of Mn doping while the porosity was increased. Temperature dependent dielectric measurements revealed that dielectric constant and dielectric loss was increased by increasing the temperature for Mn-doped samples. The conductivity was also enhanced with increasing temperature due to the enhanced evolution of charge carriers between the grains. Temperature dependent impedance spectroscopy confirmed that resistance and reactance were inverse function of the temperature revealing negative temperature coefficient of resistance. Nyquist plot shows semi-circular behavior attributed to the grain boundary effect.
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Abstract In this work, we present magnetic phase transition temperatures and magneto-dielectric coupling in MCr 2 O 4 (M = Fe, Co and Ni) ceramics, synthesized using sol–gel auto-combustion route. In order to develop their respective... more
Abstract In this work, we present magnetic phase transition temperatures and magneto-dielectric coupling in MCr 2 O 4 (M = Fe, Co and Ni) ceramics, synthesized using sol–gel auto-combustion route. In order to develop their respective crystalline textures, all these chromites were calcined at 650 °C for 2 h. X-ray diffraction patterns confirmed that FeCr 2 O 4 had a rhombohedral structure while NiCr 2 O 4 and CoCr 2 O 4 exhibited a spinel-type cubic structure. The presence of relevant elements in the specific stoichiometric ratios was confirmed using energy dispersive X-ray spectroscopy. The shapes and sizes of the grains for all the samples were determined using the images obtained from a field emission scanning electron microscope. Temperature dependent magnetic analysis have shown that FeCr 2 O 4 , CoCr 2 O 4 and NiCr 2 O 4 are ferromagnetic at 5 K and their magnetic phase transition temperatures were measured as 80, 83 and 90 K, respectively. Spin-orbit interference was also studied through magneto-dielectric coupling for these chromites using a modified impedance analyzer set-up.
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Abstract Phenol red dye (PR) functionalized mesoporous silica matrix nano-structures/ nano-tubes (MSNs) are synthesized by sol-gel method for pH sensing. FE-SEM analysis revealed formation of different nano-objects (i.e. nano-clusters and... more
Abstract Phenol red dye (PR) functionalized mesoporous silica matrix nano-structures/ nano-tubes (MSNs) are synthesized by sol-gel method for pH sensing. FE-SEM analysis revealed formation of different nano-objects (i.e. nano-clusters and nano-tubes) with defined pores, which are arranged into bunch of nanotubes after PR encapsulation. AFM analysis shows the crack-free dense matrices films with low average surface roughness and thickness. XRD and FT IR exhibited the interaction/bonding of phenolic anchoring groups of PR with silica. HRTEM analysis confirms the formation of crystalline nano-tubes after PR encapsulation within silica matrix. TGA/DTA analysis shows PR dye interacts efficiently within the silica matrix species from 300 °C - 1000 °C. N2 adsorption isotherms confirms the meso-porous nature of the PR encapsulated silica matrix have high surface area value of 434 m2/g with a pore volume of 0.96 cm3/g. UV–vis analysis exhibited that silica matrix has transmission of 84% at 550 nm and 1.36 refractive index. However, transmission is reduced to 79% whilst refractive index increased to 1.37 at 550 nm after PR encapsulation. Coated fiber optic displayed dynamic range of 1–10 pH with fast response time (
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Abstract Rare earth zirconates with pyrochlore type structure have shown a potential for practical applications due to their stable crystal structure with tunable lattice parameters. In this context, a series of Ce-substituted neodymium... more
Abstract Rare earth zirconates with pyrochlore type structure have shown a potential for practical applications due to their stable crystal structure with tunable lattice parameters. In this context, a series of Ce-substituted neodymium zirconates with general formula, Nd 2 Zr 2−x Ce x O 7 (x = 0.0, 0.4, 0.8, 1.2, 1.6, 2.0) was synthesized using wet chemical sol–gel auto-combustion technique. Structural analysis confirmed the formation of stable pyrochlore phase with space group Fd3m . The scanning electron microscopic analysis revealed that the parent compound adopted a mixed morphology (rectangular, spherical, squared etc.) with sharp grain boundaries and considerable porosity. A significant agglomeration was observed with Ce-substitution at Zr-site which improved the density of material. The stoichiometric composition of the elements present in the samples was confirmed by energy dispersive X-ray spectroscopy. The response of the material to external electric field of varying frequency was studied through impedance spectroscopy which confirmed the active contribution of grains and grain boundaries in the form of electrical response of the material. The nature of mobility of charge carriers was checked by the interaction of external varying electric field with the electric dipole moments of the material. This whole study provides valuable information about the energy storage capacity of the material and thus determines the potential of the material to be used in energy storage devices.
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Abstract As the doped semiconductors can induce and tune the novel physical characteristics. Therefore, we present the investigation of Fe doped SnS nano-crystallites, with xFe = 0.00–0.10, synthesized by using cost-effective and simple... more
Abstract As the doped semiconductors can induce and tune the novel physical characteristics. Therefore, we present the investigation of Fe doped SnS nano-crystallites, with xFe = 0.00–0.10, synthesized by using cost-effective and simple co-precipitation method. X-ray diffraction (XRD) has confirmed the orthorhombic single phase formation with nano-crystalline nature that is consistent with the surface structure revealed using SEM. NEXAFS spectroscopy has demonstrated that Fe retains +2 oxidation states. The dielectric response measured within 1 kHz-20 MHz depicts that the specimens respond well to the low energies indicating potential applications in the optical devices. Complex impedance study has elucidated dominant contribution from the grain resistance, while the complex modulus analysis confirmed the role of grains capacitance, suggesting that the polarization effect of such electrodes could have practical utilities. The ferromagnetism exhibited at 300 K also has revealed data storage device applications of the studied compounds.
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Phase stable Nd-substituted lanthanum zirconates of the form La2−xNdxZr2O7 (x = 0.0, 0.2, 0.4, 0.6 and 2.0) with tunable structural parameters, were synthesized using a cost effective, wet chemical based sol–gel auto-combustion route.... more
Phase stable Nd-substituted lanthanum zirconates of the form La2−xNdxZr2O7 (x = 0.0, 0.2, 0.4, 0.6 and 2.0) with tunable structural parameters, were synthesized using a cost effective, wet chemical based sol–gel auto-combustion route. Rietveld’s refined X-ray diffraction patterns confirmed the formation of phase pure cubic pyrochlore structure with space group Fd3m. Data obtained from the refinement revealed that Nd-substitution at La-site reduced the lattice parameters from 10.782 to 10.637 Å and thus caused the shrinkage of the unit cell volume from 1253.452 to 1203.820 Å3. Field emission scanning electron microscopy operated in back scattered electron mode at 5.0 kV confirmed that Nd-substitution promoted the grain growth (77–430 nm) and densification of the prepared ceramics. Ferroelectric analysis showed that pure as well as Nd-substituted samples exhibited leaky ferroelectric loops at room temperature however, maximum value of polarization increased with substitution. Smaller values of coercivity and remanence obtained in the magnetic investigation suggested the superparamagnetic nature of the prepared samples. A profound effect of magnetic field on dielectric properties was also observed from the magnetodielectric study. The probable origin of magnetodielectric effect is discussed on the basis of dielectric study in the presence of magnetic field.
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Abstract Fe doped ZnO nanoparticles with varying Fe concentrations 1–17% were fabricated by sol-gel route. Fourier-transform infrared spectrometer (FTIR) study established Fe doping and incorporation of Fe in ZnO lattice. X-ray... more
Abstract Fe doped ZnO nanoparticles with varying Fe concentrations 1–17% were fabricated by sol-gel route. Fourier-transform infrared spectrometer (FTIR) study established Fe doping and incorporation of Fe in ZnO lattice. X-ray diffraction (XRD) results indicated that the synthesized nano-particles were poly-crystalline with the hexagonal wurtzite structure. No impurity or iron compound peak was foud. The band gap of the synthesized nano-particles was observed to increase with the increase of Fe percentage and hence displayed a blue shift but the band gap of Fe doped ZnO is lesser than the band gap of undoped ZnO. Magnetic study assured a ferromagnetic trend for all the synthesized nano-particles due to Fe doping in ZnO. The effects of Fe percentage on the antibacterial efficiency against two different bacteria Escherichia coli (E.coli) and Pseudomonas aeruginosa (P. aeruginosa) were probed. The antibacterial efficiency was best for 14 and 17 at% of the Fe doping level. Photocatalytic activity was determined by degradation of methylene blue (MB) dye in ethanol solution under sunlight. ZnO with 1% Fe showed the better photo- catalytic property.
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Mesostructured silica-titania (ST) and bromophenol blue encapsulated silica–titania (BPB-ST) nanomatrices are synthesized by sol–gel method at low temperature. FESEM analysis shows uniform crack-free porous surface of ST matrix. EDX... more
Mesostructured silica-titania (ST) and bromophenol blue encapsulated silica–titania (BPB-ST) nanomatrices are synthesized by sol–gel method at low temperature. FESEM analysis shows uniform crack-free porous surface of ST matrix. EDX mapping analysis shows that the BPB species are uniformly distributed/immobilized throughout the ST matrix lattices. AFM images reveal 45.68 nm thick film with low average surface roughness ~1.27 nm, after encapsulation of BPB dye in ST matrix. TEM analysis exhibits uniform interior titania core and silica shell network, with average particle size 2.4 ± 0.4 nm for ST sample which reduced to 0.8 ± 0.3 nm after BPB encapsulation. Mesoporous high surface area 488 m2/g and pore volume of 0.55 cm3/g encapsulated matrix is found to be beneficial for sensing analysis. Transparent (67%) mesoporous nanoparticles with low refractive index 1.41 is obtained for encapsulated nanomatrix. The synthesized sensing material is fast responsive <1 sec and found to be linear for pH 3–12. High pKa value of 7.57 at 580 nm for ST-BPB leads to the broader sensitivity range, repetitive, easy-to use, and color indication system. The ability to change color in response to external stimulus makes ST-BPB a potential sensing material in food.Graphical abstract
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Cu-doped zinc oxide thin films are dip coated on glass substrates. Zinc acetate and copper acetate are used as metal precursors to synthesize sol. XRD scanning discloses that all films have the hexagonal wurtzite structure of ZnO. All... more
Cu-doped zinc oxide thin films are dip coated on glass substrates. Zinc acetate and copper acetate are used as metal precursors to synthesize sol. XRD scanning discloses that all films have the hexagonal wurtzite structure of ZnO. All films are a-axis oriented with preferred orientation along (101). Crystallite size of thin films increased with the increase in the Cu doping percentage from 2 to 10 wt%. TGA scrutiny predicted that weight loss takes place till 530 °C. Increase in Cu doping leads to insignificant decrease in the optical band gap of the thin films. All films show ferromagnetic properties which are due to hybridization of p–d orbitals.
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Abstract Pyrochlore structure based compounds have shown valuable interest in practical applications because of their structure tunability and stability. In this context, the stability of pyrochlore structure in a particular phase is... more
Abstract Pyrochlore structure based compounds have shown valuable interest in practical applications because of their structure tunability and stability. In this context, the stability of pyrochlore structure in a particular phase is quite essential for practical optimization of valuable dielectric and impedance characteristics of rare-earth zirconates. Thus, in the present work, a series of Nd substituted lanthanum zirconates were synthesized to investigate its effect on the structural, morphological, electrical and dielectric properties. Structural analysis confirmed the formation of sustainable pyrochlore phase in all the samples having space group Fd 3 m . A drastic reduction in grain size with Nd substitution was visualized by the images obtained using a field-emission scanning electron microscope. The electrical impedance spectroscopy was performed to check the frequency response of the dielectric behaviour, giving tenable information about changes in electrical permittivity due to Nd substitution. Impedance analysis shows a contribution of grains and grain boundaries in these heterogeneous zirconate samples. These regions are easily distinguishable in the sense of their electrical conductivity and impedance characteristics. The conductivity values obtained were lying in the range of nano-Farad predicted these materials to be used as solid oxide fuel cells.
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Abstract Owing to the excellent power density, energy storage capability, and rechargeable nature, lithium-ion batteries are being used in laptops, vehicles, home electronics and large-scale industrial instruments, and thus governing the... more
Abstract Owing to the excellent power density, energy storage capability, and rechargeable nature, lithium-ion batteries are being used in laptops, vehicles, home electronics and large-scale industrial instruments, and thus governing the market of portable electronics. Here, we present the electrochemical performance of the V2O5/acetylene black (V2O5/C) nanocomposite, used as a cathode material in lithium-ion batteries, prepared by a facile chemical synthesis route. The nanocomposite shows an outstanding electrochemical performance with a discharge capacity of 361 mAh g−1 during 1st cycle and retains a capacity of 254 mAh g−1 after 100 cycles, at a step rate of 0.1 C. Further, electrochemical impedance spectroscopy was employed to examine the reaction kinetics before and after cycling and the Li+-diffusion coefficient was calculated to be 1.67 × 10−12 and 6.13 × 10−15 cm2 s−1, respectively. The enhanced electrochemical performance of V2O5/C nanocomposite can be ascribed to the synergistic effect of nanosized V2O5 and conductive acetylene black, which could shorten diffusion pathway, play a role of efficient charge carrier and make the electrode have better electronic/ionic conductivity and lower resistance. Hence, V2O5/C nanocomposite could be utilised as promising cathode material for lithium-ion batteries because of its stable electrochemical performance.
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Abstract Ni doped Cr 2 O 3 (NCO) films have attracted much attention due to their applications in the field of photovoltaics. This study reports the tailoring of structural, electrical and optical properties as a function of Ni doping in... more
Abstract Ni doped Cr 2 O 3 (NCO) films have attracted much attention due to their applications in the field of photovoltaics. This study reports the tailoring of structural, electrical and optical properties as a function of Ni doping in Chromium oxide (Cr 2 O 3 ). NCO thin films were grown by Pulsed laser deposition (PLD) using 2nd harmonic Nd:YAG Laser on n-Si (100) with in-situ annealing of 450 °C. Structural analyses based on X-ray diffractometry (XRD) and Raman Spectroscopy showed the inconsistent variation in crystallinity and shift in A 1 g band in turn revealing the successful incorporation of Ni into Chromium oxide host lattice. In addition, electrical measurements also showed an inconsistent variation in resistivity ranging from 10 2 to 10 4 Ω − cm . The properties showed widening of band gap energy (E g ) from 3.41 to 3.60 eV as a function of Ni doping concentration with significantly decreased reflectance in the range of 500–600 nm thereby increasing the absorption, a pre-requisite for solar absorbers.
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Abstract In this letter, we demonstrate an apparent magnetically activated electric polarization reorientation at room temperature through magneto-electric coupling in (1 − x)BiFeO3–xPbTiO3 (x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5)... more
Abstract In this letter, we demonstrate an apparent magnetically activated electric polarization reorientation at room temperature through magneto-electric coupling in (1 − x)BiFeO3–xPbTiO3 (x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) composites. A change in magnetic field causes variation in electric polarization, attributed to the destruction of space modulated spin antiferromagnetic structure with the PbTiO3 addition. This behavior also results in the increase in magnetic parameters as the coercive field of the composites increases with the increase in PbTiO3 contents. The analysis demonstrates that the magneto-electric coupling in the prepared ferromagnetic/ferroelectric composites is dominant at room temperature, quite feasible for modern day devices.
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Abstract Bismuth iron oxide sols are synthesized using microwave radiations with variation in microwave power in the range of 180 W–1000 W. Magnetic analysis of bismuth iron oxide sols indicate ferromagnetic behavior at microwave powers... more
Abstract Bismuth iron oxide sols are synthesized using microwave radiations with variation in microwave power in the range of 180 W–1000 W. Magnetic analysis of bismuth iron oxide sols indicate ferromagnetic behavior at microwave powers of 540–720 W. Paramagnetic behavior is observed at microwave powers of 180 W and 270 W. Mixed ferromagnetic and antiferromagnetic behavior of sols is obtained at microwave power of 360 W, 450 W and 810 W–1000 W. Sols synthesized using microwaves are spin coated onto copper substrates and annealed at 300 °C, in the presence of magnetic field, to obtain bismuth iron oxide thin films. X-ray diffraction patterns of thin films indicate amorphous behavior at low microwave power of 180 W and 270 W. Mixed BiFeO3 and Bi25FeO40 phases are obtained at microwave powers of 360 W and 450 W. Transition to phase pure BiFeO3 takes place at microwave power of 540–720 W. Mixed BiFeO3 and Bi2Fe4O9 phases are obtained at high microwave powers of 810 W–1000 W. Energy dispersive X-ray spectrum also confirms formation of BiFeO3 phase with 66.21%, 17.63% and 15.20% for Bi, Fe and O, respectively. Strong ferromagnetic behavior with low magnetocrystalline anisotropy is observed for films prepared using microwave power of 540–720 W. High saturation magnetization of 26.38 emu/cm3 is obtained at microwave power of 720 W. Field cooled and zero-field cooled magnetization curves show spin orientation transition at ∼80 K. Low temperature Raman analysis indicates presence of electromagnons with anomaly observed at 80 K.
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Zirconium Titanium dioxide (TiO: Zr) thin films were synthesized on glass substrates by the dip coating technique. The structural, optical, magnetic, photo-catalytic and antibacterial properties were explored for the films synthesized... more
Zirconium Titanium dioxide (TiO: Zr) thin films were synthesized on glass substrates by the dip coating technique. The structural, optical, magnetic, photo-catalytic and antibacterial properties were explored for the films synthesized with zirconium concentration 10, 15, 20, 25 and 30 at.%. X-ray diffraction (XRD) revealed that the thin films contain anatase-rutile-brookite TiO and cubic-ZrO phases. Moreover, it was noticed that ZrO retarded the anatase-to-rutile transformation at high Zr doping percentage.The crystallite size of ZrO phase was in the range of 10.93-18.22 nm, whereas it was in the range of 13.5-21.59 nm for TiO phase for same Zr doping percentage. The band gap of films was in the range of 2.99-3.17 eV. The band gap value decreased with increase in Zr-doping percentage due to the creation localized levels near the conduction band providing a large number of electrons to reach the conduction band. Films showed room temperature ferro-magnetism due to the defects produce...
Research Interests: Materials Science, Titanium, Medicine, Metal Nanoparticles, Differential scanning calorimetry, and 12 moreReactive Oxygen Species, Escherichia coli, Thin Film, Pseudomonas aeruginosa, Thermogravimetry, Anti-Bacterial Agents, X ray diffraction, Particle Size, Zirconium, Fourier transform infrared spectroscopy, Pseudomonas Aeruginosa, and Biochemistry and cell biology
In the present work, Zinc Sulphide (ZnS) thin films deposited by resistive heating technique on BK-7 glass substrate. Optical and structural characterizations of ZnS films have been carried out along with the post-deposition annealing at... more
In the present work, Zinc Sulphide (ZnS) thin films deposited by resistive heating technique on BK-7 glass substrate. Optical and structural characterizations of ZnS films have been carried out along with the post-deposition annealing at different temperatures. The thickness of the film is monitored by quartz crystal monitor and found to be 500[Formula: see text]nm. Fourier transform infrared (FTIR) spectroscopy provides the qualitative analysis of ZnS film before and after annealing at different temperatures. The optical investigation shows that the as-deposited and annealed ZnS film display the high optical transmittance of (64–68%) in the visible/near infrared region. The optical energy gaps of present as-deposited and annealed ZnS film vary in the range of 3.32–3.18[Formula: see text]eV with the change in annealing temperature.
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We have fabricated Zn[Formula: see text]FexS ([Formula: see text], 0.02, 0.04, 0.06, 0.08 and 0.10) diluted magnetic semiconductors using co-precipitation method. X-ray diffraction patterns depict that Zn[Formula: see text]FexS appears as... more
We have fabricated Zn[Formula: see text]FexS ([Formula: see text], 0.02, 0.04, 0.06, 0.08 and 0.10) diluted magnetic semiconductors using co-precipitation method. X-ray diffraction patterns depict that Zn[Formula: see text]FexS appears as a dominant phase with cubic zinc blende structure and nanoscale crystallite size. In addition, a secondary phase of rhombohedral ZnS also appears; however, no additional phase arises that primarily belongs to Fe dopant. Using Debye–Scherrer relation, the crystallite size is found to be in the range of 20–27[Formula: see text]nm, which is in good agreement with the crystallite size calculated using the Williamson–Hall (WH) plot method. The appearance of secondary phase provoked to study the residual strain using Stokes–Wilson equation, which is nearly consistent to that observed using WH plot method. The surface morphology, revealed using scanning electron microscopy, depicts non-uniform surface structure with a variety of grains and void dimensions...
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ABSTRACT Zirconia ceramics have gained lot of interest as restorative materials because of remarkable mechanical properties; such as high strength and toughness, good biocompatibility, and aesthetic properties. But the problem with... more
ABSTRACT Zirconia ceramics have gained lot of interest as restorative materials because of remarkable mechanical properties; such as high strength and toughness, good biocompatibility, and aesthetic properties. But the problem with zirconia is inertness with the body fluid and it resists the formation of bonds with bones and tissues. This problem can be minimized by using some biocompatible additives. This explorative study was performed to examine a possible impact of organic additives’ ratio on ZrO2 thin films. Glucose, fructose and water were added into pre-synthesized zirconia with variation in ratio from 1:1:5 to 1:1:25. Formation of pure tetragonal phase was investigated at glucose: fructose: water ratio of 1:1:10 by X-ray diffractometer. As the water content increases adsorption of OH ions produces tensile stresses which lead to transformation of pure tetragonal phase to monoclinic phase. The mechanical properties of the samples were characterized by Micro Vickers hardness tester and hardness of the samples is in the range of 565-1,053 HV. High value of hardness and low value of porosity has been observed in thin film with glucose: fructose: water ratio of 1:1:10. Surface morphology of thin films is observed by scanning electron microscope. Fourier transform infrared spectroscopy study presents the formation of tetragonal zirconia bond with presence of OH ion. Relatively weak bond of C-H bonding was formed; indicating the presence of organic additives in ZrO2. High temperature tetragonal phase has been obtained in as-deposited thin film using water-soluble and body fluid compatible organic additives without any heat treatment. Hence, these as-deposited thin films, with pH 5.5, have potential application as protective coatings on teeth.
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Zirconia (ZrO2) is one of the most well studied transition-metal oxides in the optical and biological fields. The applications area of ZrO2 can be increased by addition of metal oxides. Aim of this study is to determine the effect of... more
Zirconia (ZrO2) is one of the most well studied transition-metal oxides in the optical and biological fields. The applications area of ZrO2 can be increased by addition of metal oxides. Aim of this study is to determine the effect of acidic and basic Fe3O4 nanoparticles’ (NPs) doping in sol–gel synthesized ZrO2. Different samples are prepared by varying Fe3O4 concentrations, acidic and basic, in the range of 2–10 wt%. Sols of Fe3O4 doped ZrO2 (FOZ) are spin coated onto glass substrates at 3000 rpm for 30 s. FOZ films are annealed at 300 °C for 1 h. It is worth mentioning that Fe3O4 nanoparticles (acidic and basic) are used for the first time, to the best of our knowledge, to stabilize zirconia using sol–gel technique. Moreover, completely homogenous FOZ sol is obtained using water as a solvent. X-ray diffraction results confirm the formation of phase pure tetragonal ZrO2 (t-ZrO2) along with less intense peak of Fe3O4 at 8–10 wt% of basic dopant. Optical spectra reveal that energy band gap lies in the range of 4.8 to 5.0 eV whereas, high value of transmission up to 80 % has been observed in case of basic dopant. Refractive indices vary with the variation in crystal structure and density of the films. Redshift is observed in Fe3O4 doped zirconia. Hardness of the samples is in the range of 310 to 962 HV.
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In this study, we have prepared Mn-doped zinc sulfide diluted magnetic semiconductors with varying manganese concentrations (xMn = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10 mol%) using co-precipitation method. The single-phase nano-crystalline... more
In this study, we have prepared Mn-doped zinc sulfide diluted magnetic semiconductors with varying manganese concentrations (xMn = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10 mol%) using co-precipitation method. The single-phase nano-crystalline Zn1−xMnxS powders have been confirmed with X-ray diffraction. The residual strains also have been calculated, and have been observed to affect the lattice constants. The surface morphology is investigated with scanning electron microscopy, which illustrates the presence of smaller grains, which coalescence to form larger grains. The presence of the ferromagnetism at room temperature has been observed; however, significant paramagnetic contribution is also present. The observed weak ferromagnetism might be due to the structural and surface imperfections. The single-phase Zn1−xMnxS exhibiting magnetism at room temperature evidences the potential spintronic applications.
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ABSTRACT
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Doping-induced tuning of host semiconductors properties offers an efficient way to realize the desired physical properties. In this study, we have synthesized pure and Co-doped SnS-diluted magnetic semiconductors with xCo = 0.00–0.10, by... more
Doping-induced tuning of host semiconductors properties offers an efficient way to realize the desired physical properties. In this study, we have synthesized pure and Co-doped SnS-diluted magnetic semiconductors with xCo = 0.00–0.10, by employing a very simple and low-cost chemical co-precipitation technique. The structural properties, determined through X-ray diffraction, have confirmed single-phase orthorhombic structure and have depicted nano-crystallites. Near-edge X-ray absorption fine structure spectroscopy has revealed a Co-doping-induced shift in the absorption edge towards lower energy, indicating a change in the Co oxidation state. Surface morphology observed through scanning electron microscopy indicates nano-structured surface. Dielectric properties measured by impedance analyzer (LCR meter) in the frequency range 1 kHz–20 MHz depict that grown materials respond to the electromagnetic radiations suggesting potential device applications. Complex impedance spectroscopy illustrates the dominance of grain resistance. The magnetic properties observed by vibrating sample magnetometer reveal room temperature ferromagnetism, and Co ions inducing tuning of the ferromagnetism suggests potential applications in the data storage devices.
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Abstract In this study we present a new nanocomposite electrolyte based on samarium (Sm) and germanium (Ge) co-doped ceria Ce 0.7 Sm 0.15 Ge 0.15 O 2-δ (SGeDC). The nanocomposite electrolyte was prepared using co-precipitation method. The... more
Abstract In this study we present a new nanocomposite electrolyte based on samarium (Sm) and germanium (Ge) co-doped ceria Ce 0.7 Sm 0.15 Ge 0.15 O 2-δ (SGeDC). The nanocomposite electrolyte was prepared using co-precipitation method. The crystal structure and surface morphology were determined using x-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Four probe dc conductivity indicated the value of 0.074 S/cm at 650 °C. The Fuel cell performance was carried out using hydrogen as fuel. The maximum OCV observed was 0.95 V while the peak power density came out to be 600 mW/cm 2 at 600 °C. It is suggested that adding Ge, the conductivity as well as performance of this new nanocomposite electrolyte is comparatively enhanced and it can find potential applications in low temperature solid oxide Fuel cells (LTSOFCs).
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Abstract Conditions were optimized to prepare SrMnO 3 via sol-gel auto-combustion route, by varying calcination temperature from 600 to 1200 °C. Single phase synthesis was confirmed by X-ray diffraction in the sample calcined at 1000 °C... more
Abstract Conditions were optimized to prepare SrMnO 3 via sol-gel auto-combustion route, by varying calcination temperature from 600 to 1200 °C. Single phase synthesis was confirmed by X-ray diffraction in the sample calcined at 1000 °C for 4 h. Rietveld’s refinement was performed to obtain the detailed information regarding the structural parameters of the manganite sample. The effect of calcination temperature on dielectric, and impedance studies has been reported from a low (20 Hz) to a high frequency region (20 MHz) SrMnO 3 ceramic samples. The dielectric response reveals electroactive regions in accordance with the Maxwell-Wagner model while the impedance analysis shows the dominant behaviour of microstructural grain boundaries. The resistive parameters were then optimized to calculate the grain/grain boundary capacitance. A possible combination of equivalent circuit is also fitted in order to determine the deviation from idealistic behaviour in impedance analysis. These circuits are also verified through frequency dependent conductivity response while the dependence of capacitance on temperature gives the information on the possible ferroelectric behaviour.
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Abstract In this paper, three composite electrolytes (Ce0.8Sm0.2O1.9/Na2CO3) SDC, (Ce0.8Gd0.2O1.9/Na2CO3) GDC and (La0.8Sr0.2Ga0.8Mg0.2O3−δ/Na2CO3) LSGM have been studied to review the effect of Na2CO3, present as second phase, and effect... more
Abstract In this paper, three composite electrolytes (Ce0.8Sm0.2O1.9/Na2CO3) SDC, (Ce0.8Gd0.2O1.9/Na2CO3) GDC and (La0.8Sr0.2Ga0.8Mg0.2O3−δ/Na2CO3) LSGM have been studied to review the effect of Na2CO3, present as second phase, and effect of Ni support, sintering and pressure for dry pressing for fuel cell performance. The electrolytes were prepared through a co-precipitation method. Different techniques were used to characterize the prepared electrolytes. The crystal structures were determined using x-ray diffraction (XRD) and structural morphologies were analyzed through scanning electron microscopy (SEM). The four-probe dc conductivity and two probe AC impedance analysis were carried out in open air. The fuel cell performance was determined with and without Ni support on anode side which resulted in a considerable difference in obtained peak power densities. It is suggested that prepared electrolytes can find potential applications in low temperatures Solid Oxide Fuel Cells (LT-SOFCs).
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Abstract Eliminating the undesirable pyrochlore phase is quite essential in order to determine the viable dielectric and magnetic characteristics of perovskite-based materials. In this work, we report the synthesis of stoichiometric... more
Abstract Eliminating the undesirable pyrochlore phase is quite essential in order to determine the viable dielectric and magnetic characteristics of perovskite-based materials. In this work, we report the synthesis of stoichiometric Sr-substituted barium manganite namely, Ba 1−x Sr x MnO 3 (x = 0.0, 0.2, 0.4, 0.6 and 0.8) to reveal the improved structural, dielectric and magnetic properties with increase in Sr contents. X-ray diffraction and subsequent Rietveld refinement reveals that with successful substitution of Sr at Ba-site, the pyrochlore phase diminishes and pure perovskite phase is achieved. Scanning electron microscopy demonstrates gradually improved grain shapes and uniformity in sizes in the series. Electrical impedance spectroscopy was performed using an impedance analyzer, to obtain frequency response of dielectric constant, giving tenable information about a sustainable change in electrical permittivity due to Sr-substitution which could be used for multilayered chip inductors. Dense dielectric materials with low losses are credible for multilayered components which make these oxides more feasible than ferrites to be used as sheets inside the multilayered chip inductors. Contribution of grains and grain boundaries effect on electrical resistivity, losses and quality factors are also distinguished. The coupling between the magnetic and dielectric order is also confirmed through magneto-dielectric measurement. Low temperature magnetic studies reveals the multiferroic characteristic of the material as the ferromagnetic transition temperature of 55 K, found experimentally has never been reported before.
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A Sol-gel dip coating route has been employed to synthesize cobalt oxide thin films on glass substrates. The obtained films are characterized by X-ray diffraction (XRD), UV-VIS spectrophotometer, vibrating sample magnetometer (VSM),... more
A Sol-gel dip coating route has been employed to synthesize cobalt oxide thin films on glass substrates. The obtained films are characterized by X-ray diffraction (XRD), UV-VIS spectrophotometer, vibrating sample magnetometer (VSM), Scanning Electron Microscope and Fourier Transform Infra Red (FTIR) spectroscopy. The films are identified as Co 3 O 4 by FTIR. XRD further confirmed Co 3 O 4 phase. Upon increasing withdrawal speed of substrate, the transmission and band gap decreases due to increase in film thickness. Thin films show room temperature ferromagnetism and magnetic properties enhance by increasing thickness of thin films. SEM shows porous surface of films.
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The mesoporous SiO 2-TiO 2 nano-composite was obtained via the sol – gel method. The presence of surfactant additive CTAB as structure-directing agent leads to the textural modification of composite network after heat treatment at 150°C... more
The mesoporous SiO 2-TiO 2 nano-composite was obtained via the sol – gel method. The presence of surfactant additive CTAB as structure-directing agent leads to the textural modification of composite network after heat treatment at 150°C for 2 hrs. The both samples before and after heat treatment were characterized by BET method, nitrogen adsorption–desorption methods and UV-Vis Spectroscopy. N2 adsorption isotherms of the annealed sample explaining the high surface area value of silica-titania nano-composite is 401m 2 /g with a pore size of 3.3 nm and pore volume of 0.33 cm 3 /g. The influence of surfactant CTAB on the pore structure and surface area of sol-gel based silica-titania nano-composite for pH sensing applications were also investigated. Furthermore, the EDX analysis substantiated the stiociomatric formation of encapsulated silica-titania nano-composites.
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In the present work, TiO 2 nanoparticles have been prepared by a sol-gel auto-combustion method using titanium tetrachloride as a precursor material, with an aim to get the anatase phase for the photocatalytic applications. Six samples... more
In the present work, TiO 2 nanoparticles have been prepared by a sol-gel auto-combustion method using titanium tetrachloride as a precursor material, with an aim to get the anatase phase for the photocatalytic applications. Six samples were prepared using three different fuel materials i.e., citric acid, urea and glycine, respectively. First three samples were obtained without thermal treatment and last three samples were obtained by sintering the first three samples at 350 °C, using the same three fuel materials. X-ray diffraction revealed that thermally sintered samples were consisting of pure anatase phase. The dielectric parameters were found to decrease with increase in frequency depicting characteristic oxide behaviour. It has been observed that the sample prepared using urea as a fuel material and subsequently sintered at 350 °C revealed better structural and electrical behaviour characteristic of pure anatase phase of TiO 2. The morphology was examined by scanning electron microscope and growth of particles was found to be much uniform for the sample obtained by using glycine as fuel material.
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Multiferroic materials like Bismuth Iron Oxide (BiFeO 3), YMnO 3 , BiMnO 3 , TbMnO 3 has attracted worldwide attraction due their applications in data storage devices, spintronic devices, sensors and multiple stage memories. Among these... more
Multiferroic materials like Bismuth Iron Oxide (BiFeO 3), YMnO 3 , BiMnO 3 , TbMnO 3 has attracted worldwide attraction due their applications in data storage devices, spintronic devices, sensors and multiple stage memories. Among these materials BiFeO 3 is a promising candidate as it exhibits room temperature antiferromagnetic and ferroelectric properties. However, BiFeO 3 suffers from some drawbacks including weak magnetic behavior, inhomogeneity in spin structure and large leakage current. In order to overcome these problems we here report Lanthanum (La) doped Bi 1-x La x FeO 3 (where, x=0.0-0.5) thin films prepared by sol-gel method. The effect of La substitution on structural and dielectric properties has been investigated. The films show pure phase rhombohedrally distorted perovskite structure of BiFeO 3. XRD peak shifts to high angles due to slight difference in ionic radii of La 3+ (1.16Å) and Bi 3+ (1.17Å). The dielectric constant and tangent loss decreases as frequency increases and becomes constant at high frequencies showing normal dispersion behavior for all concentrations (i.e. x=0.0-0.5). The dispersion in dielectric constant occurs due to the time required by the carriers to get align in the direction of field. At high frequencies the field reversal is so high that the carriers do not get enough time to get aligned in the direction of field thus resulting in low dielectric constant at high frequency. The dielectric constant is strongly affected by changes in grain size. Decrease in grain size leads to increase in number of grain boundaries hindering the hopping process between the different states and grains thus resulting in accumulation of cations at the grain boundaries thus affecting the dielectric constant.
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During the past few years, multiferroic materials i.e. materials exhibiting ferroelectricity and ferromagnetism have acquired worldwide attraction due to its wide range of applications in devices as small as sensors to devices as large as... more
During the past few years, multiferroic materials i.e. materials exhibiting ferroelectricity and ferromagnetism have acquired worldwide attraction due to its wide range of applications in devices as small as sensors to devices as large as transformers. Among various multiferroic materials, bismuth iron oxide is a promising candidate. However, there are some drawbacks associated with phase pure BiFeO 3 including volatility of Bi 2 O 3 , large leakage current and antiferromagnetic/ weak ferromagnetic behavior. In this work bismuth iron oxide nanoparticles (NPs) are synthesized using sol-gel technique. NPs are calcined at 100˚C, 200˚C and 300˚C. Bismuth iron oxide NPs are characterized using x-ray diffractometer, vibrating sample magnetometer and impedance analyzer. NPs show amorphous behavior under as-prepared conditions. Dielectric constant increases from 49 to 74 (at frequency = 1MHz) and tangent loss decreases from 0.2 to 0.012 with increase in calcination temperature from 100-300˚C. Ferromagnetic behavior instead of antiferromagnetic nature of bulk bismuth iron oxide arises due to suppression of helical spin structure. The suppression of spin structure leads to ferromagnetic behavior with saturation magnetization of 7.125×10-4 emu, 1.28×10-3 emu and 1.59×10-3 emu at 100˚C, 200˚C and 300˚C.
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In order to obtain a bioactive material; with high mechanical strength, high fracture toughness and aesthetic properties needs to be fabricated. Such properties can be obtained in ceramics. Zirconia ceramics have gained favor as... more
In order to obtain a bioactive material; with high mechanical strength, high fracture toughness and aesthetic properties needs to be fabricated. Such properties can be obtained in ceramics. Zirconia ceramics have gained favor as restorative materials because of their excellent mechanical properties; they have high strength and toughness, good biocompatibility, and relatively good aesthetic properties. But the problem with zirconia is inertness with the body fluid and it resists the formation of bonds with bones and tissues. This problem can be minimized by some biocompatible additives. This explorative study was performed to examine a possible impact of polymer on ZrO 2 nanoparticles (NPs). Along with effect of reaction temperature (50, 100 and 150°C) has been investigated on structural and mechanical properties of polymer additive zirconia. XRD results illustrate the partially stabilized zirconia (PSZ) however, monoclinic content decreases with increase in reaction temperature. A decrease in crystallite size has observed due to structural changes. A decrease in particle size has found at higher reaction temperatures. The mechanical properties of the samples were characterized by Micro Vickers Hardness tester and hardness of the samples is in the range of 590HV to 1000HV.
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In the present study sol–gel method has been employed using polymers additives to deposit zirconia thin films. Effect of reaction temperature (50, 100 and 150°C) have been investigated on structural and mechanical properties of zirconia... more
In the present study sol–gel method has been employed using polymers additives to deposit zirconia thin films. Effect of reaction temperature (50, 100 and 150°C) have been investigated on structural and mechanical properties of zirconia thin films. Addition of polymers has prominent effect on structural and mechanical properties of zirconia. Phase analysis was executed by X-Ray diffractrometer (XRD). Formation of tetragonal zirconia (t-ZrO 2) along with monoclinic content has been observed at relatively higher reaction temperatures (100 and 150°C). A sharp decrease in crystallite has observed at reaction temperature 100°C. Higher reaction temperatures cause volume shrinkage due to removal of hydroxyl (OH) ions since OH ions are responsible for monoclinic content. Removal of OH ions at relatively higher reaction temperatures leads to presence of tetragonal zirconia at room temperature. Hardness of the polymer additive zirconia has obtained up to 850HV confirmed by Micro Vickers hardness indenter. These as deposited thin films with presence of tetragonal content can be successfully employed for teeth coatings.
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We here report the preparation and characterization of cobalt doped iron oxide nanoparticles using sol-gel method. The dopant concentration is varied as 2%, 4%, 6%, 8% and 10%. The position of diffraction peaks shifts to slightly higher... more
We here report the preparation and characterization of cobalt doped iron oxide nanoparticles using sol-gel method. The dopant concentration is varied as 2%, 4%, 6%, 8% and 10%. The position of diffraction peaks shifts to slightly higher angles due to smaller ionic radii of cobalt as compared to that of iron. No peaks corresponding to cobalt or cobalt oxide are observed indicating that dopant has been successfully incorporated in the host lattice. Cobalt with electronic configuration of [Ar]3d 7 4s 2 has one more electron than iron. Cobalt atom donates one d and two s electrons to oxygen that results in remaining six electrons on cobalt. When Co is substituted for Fe with spin down electron the spin down d band gets completely filled with remaining one d-electron residing in spin up band. This results in increase in net magnetization in cobalt doped iron oxide nanoparticles as compared to undoped iron oxide nanoparticles.
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Amongst various phases of iron oxide, hematite (α-Fe 2 O 3) has attracted world attraction due wide range of technological and industrial applications including spintronic and data storage devices. However hematite exhibits weak... more
Amongst various phases of iron oxide, hematite (α-Fe 2 O 3) has attracted world attraction due wide range of technological and industrial applications including spintronic and data storage devices. However hematite exhibits weak ferromagnetic behavior at room temperature. For enhancing the magnetic properties of hematite nanoparticles we here report structural and magnetic properties of Cr doped Fe 2 O 3 nanoparticles prepared using sol-gel method. The dopant concentration is varied as 2%, 4%, 6%, 8% and 10%. The nanoparticles are characterized using Bruker D8 Advance X-ray Diffractometer (XRD) and Lakeshore's 7407 Vibrating Sample Magnetometer (VSM). Presence of (012), (104), (110), (113), (024), (116), (214) and (300) planes in XRD indicate the formation of Fe 2 O 3 phase. XRD results indicate that incorporation of chromium causes contraction in unit cell that shifts the peak positions to higher diffraction angles. Undoped iron oxide nanoparticles show weak ferromagnetic behavior because of the presence of uncompensated magnetic moments between two sublattice that give rise to canting of spin structure. Incorporation of chromium in the host hematite lattice leads to appearance of localized magnetic moments in hematite nanoparticles thus leading to increase in magnetic properties. At high dopant concentration, Cr atoms can go to the interstitial positions thus, possibility of having free Cr atoms at high dopant concentration lead to the distortion of magnetic behavior.
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The un-doped and Fe-doped ZnS nanocrystalline thin films were deposited on glass substrates by chemical bath deposition (CBD). Iron chloride, zinc chloride and thioacetamide were used as precursors and de-ionized water was used as... more
The un-doped and Fe-doped ZnS nanocrystalline thin films were deposited on glass substrates by chemical bath deposition (CBD). Iron chloride, zinc chloride and thioacetamide were used as precursors and de-ionized water was used as solvent. The synthesis and deposition of thin films was carried out without using any surfactant/capping agent. The powder X-ray diffraction patterns reveal the formation of cubic zinc blende phase of ZnS in all cases. The incorporation of iron in ZnS lattice was confirmed by the change in lattice parameters accordingly with doping concentration and absence of traces of secondary phases or Fe clusters. The M-H curves indicate that doped ZnS thin films exhibit room temperature ferromagnetism. The magnetization properties as a function of field angle and doping concentration were studied in detail. The density functional calculations were performed using Full Potential Linearized Augmented Plane Wave (FPLAPW) as is employed in elk-code. The strong p-d hybridization observed between sulphur and iron result in ferromagnetic stable state and half metallicity in these materials. The half metallic iron doped ZnS thin films can have applications in future spintronic devices. 1. INTRODUCTION The research interest is focused during the last decade on the experimental and theoretical study of DMSs offering T c above room temperature. The T c of II-VI semiconductors (ZnS and CdS) based DMS is found to be very close to room temperature and can be adjusted by the different synthesis parameters especially the dopant concentration. The Mn doped InAs was reported as DMS with T c above room temperature (Holub 2004). The ZnS being an important II–VI compound semiconductor with direct wide band gap may be expected to be ferromagnetic at room temperature. The transition metal doped ZnS are found to be half metallic when doped with Cr, Fe, and Ni while maintain its semiconducting nature when doped with Mn and Co (Stern 2004 and McNorton 2008). Tablero (2006) found that ZnS doped with Cr has a partially filled intermediate band for both FM and AFM spin alignments.
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Maghemite (γ-Fe 2 O 3) is one of the promising candidates for its use in biomedical and in optoelectronics. Density functional theory (DFT) with generalized gradient approximation (GGA:PBE) is used in order to study structural and optical... more
Maghemite (γ-Fe 2 O 3) is one of the promising candidates for its use in biomedical and in optoelectronics. Density functional theory (DFT) with generalized gradient approximation (GGA:PBE) is used in order to study structural and optical properties of iron oxide. By using BAND tool with basis set of TZ2P, geometry optimization is achieved. Cubic spinel structure is confirmed after geometry optimization with bond length of 3.55 Å between iron and oxygen in γ-Fe 2 O 3. Amount of Hirshfeld charge is observed to be 18.02, 28.39 for Fe(1) and Fe(2), respectively instead of 26.00. While for all three oxygen atoms its value increases from 8.00 to 9.85. Indirect band gap of γ-Fe 2 O 3 is observed with value of 0.68 eV without applying Hubbard potential U. After applying Hubbard potential U=3 band gap of 2.1eV is achieved which is in agreement to the experimental value of 2.0 eV (Zhu et al. 2013). Total density of states along with partial density of states for iron and oxygen is also studied. It is important to mansion it here that it is the first time to use Amsterdam Density Functional software to investigate properties of maghemite and all these calculations were carried out at 0K.
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Cubic FeO has been studied by using density functional theory. Generalized gradient approximation (GGA:PBE) and local density approximation (LDA) is used in order to study optical and structural properties of iron oxide. By using BAND... more
Cubic FeO has been studied by using density functional theory. Generalized gradient approximation (GGA:PBE) and local density approximation (LDA) is used in order to study optical and structural properties of iron oxide. By using BAND tool with basis set of TZ2P geometry optimization is achieved and fcc structure is observed. It is important to mention it here that all the calculations were taken at 0K by using Amsterdam density functional software for the first time to investigate structural and electronic properties of FeO (wüstite). Band gap of 0.615 eV and 0.75 eV is observed by GGA and LDA. While, 2.2 eV and 1.89 eV is obtained by GGA+U and LDA+U respectively. Constant value of Hubbard potential (U) is used for both approximations i.e. 6.4 eV. Total DOS and partial density of states for iron and oxygen is also studied for both approximations. Analysis of the density of states confirms the strong hybridization between Fe 3d and O 2p states in FeO. The bond length between iron and oxygen is examined and found to be 3.74Å with total bonding energy of 15.99 eV.
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Iron Oxide has gained much interest in biomedical and spintronics applications due to its unique and novel properties. Amsterdam density functional (ADF) software is used for the first time in order to theoretically investigate the... more
Iron Oxide has gained much interest in biomedical and spintronics applications due to its unique and novel properties. Amsterdam density functional (ADF) software is used for the first time in order to theoretically investigate the structural properties of cobalt doped iron oxide at 0K. TZ2P is used as basis set. Using GGA geometry optimization was achieved to observe structural properties. Inverse spinel cubic structure with lattice parameter of 8.39 Å is confirmed after geometry optimization by using GGA. 2X1X1 super cell of cobalt doped iron oxide is formed and GGA:PBE method is used to obtain total density of states (DOS) along with partial DOS of iron, cobalt and oxygen, respectively. Increase in band gap energy at 0K is observed after applying Hubbard potential (U=3 and 4 eV) for cobalt and iron, respectively.
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Multiferroic materials like Bismuth Iron Oxide (BiFeO 3), YMnO 3 , BiMnO 3 , TbMnO 3 has attracted worldwide attraction due their applications in data storage devices, spintronic devices, sensors and multiple stage memories. Among these... more
Multiferroic materials like Bismuth Iron Oxide (BiFeO 3), YMnO 3 , BiMnO 3 , TbMnO 3 has attracted worldwide attraction due their applications in data storage devices, spintronic devices, sensors and multiple stage memories. Among these materials BiFeO 3 is a promising candidate as it exhibits room temperature antiferromagnetic and ferroelectric properties. However, BiFeO 3 suffers from some drawbacks including weak magnetic behavior, inhomogeneity in spin structure and large leakage current. In order to overcome these problems we here report Lanthanum (La) doped Bi 1-x La x FeO 3 (where, x=0.0-0.5) thin films prepared by sol-gel method. The effect of La substitution on structural and dielectric properties has been investigated. The films show pure phase rhombohedrally distorted perovskite structure of BiFeO 3. XRD peak shifts to high angles due to slight difference in ionic radii of La 3+ (1.16Å) and Bi 3+ (1.17Å). The dielectric constant and tangent loss decreases as frequency increases and becomes constant at high frequencies showing normal dispersion behavior for all concentrations (i.e. x=0.0-0.5). The dispersion in dielectric constant occurs due to the time required by the carriers to get align in the direction of field. At high frequencies the field reversal is so high that the carriers do not get enough time to get aligned in the direction of field thus resulting in low dielectric constant at high frequency. The dielectric constant is strongly affected by changes in grain size. Decrease in grain size leads to increase in number of grain boundaries hindering the hopping process between the different states and grains thus resulting in accumulation of cations at the grain boundaries thus affecting the dielectric constant.
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The availability of zirconium dioxide (zirconia) ceramics in dentistry has expanded the range of designs and applications for all-ceramic restorations and increased its popularity. Nanoparticles (NPs) have attracted considerable attention... more
The availability of zirconium dioxide (zirconia) ceramics in dentistry has expanded the range of designs and applications for all-ceramic restorations and increased its popularity. Nanoparticles (NPs) have attracted considerable attention owing to their unique properties and ease of production from variety of materials. Zirconia with enhanced properties can be achieved by doping with biocompatible material. The present study devised sol gel method for preparation of Fe 3 O 4 doped ZrO 2 nanoparticles (NPs). Zirconia sol is doped with pre-synthesized Fe 3 O 4 NPs. Structural characterizations have shown a mixture of monoclinic and tetragonal zirconia. An increase in crystallite size has observed with dopant concentration. Lattice contraction was observed for the Fe 3 O 4-doped zirconia samples. This lattice contraction results in volumetric change which leads to formation of tetragonal phase. Relative higher density (~6g/cm 3) has been observed which is perquisite for implantations and coatings. Magnetic properties reveal the mix paramagnetic and ferromagnetic behavior with low value of coercivity and magnetization.
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ZnO semiconductor is a potential candidate for the information processing, energy storage, communication and optoelectronic devices. Various physical properties of the ZnO have been demonstrated both experimentally and theoretically. We... more
ZnO semiconductor is a potential candidate for the information processing, energy storage, communication and optoelectronic devices. Various physical properties of the ZnO have been demonstrated both experimentally and theoretically. We reported the different characteristics of undoped and Indium doped ZnO using first principle calculations under the framework of density functional theory. Both wurtzite and zincblende phases of the ZnO are examined using local density approximations (LDA) and generalized gradient approximation (GGA) with different exchange correlation potential within DFT for band structure calculations. Results reveal that the pure ZnO is a direct band gap semiconductor which can be employed for wide range of optoelectronics devices. The accuracy of the results are also checked with reported experimental data which are in consistent. We investigated Indium metal doped ZnO, in order to explore the influence of the doping on structural and optical properties. The band structure and total density of states for various percentages of Indium (x = 0, 0.25, 0.50 and 0.75) in ZnO are calculated with the help of density function theory. Calculations revealed the shifting of Fermi level in the conduction band with increasing indium concentrations. The conductivity are also examined with different percentages of Indium. The results also compared with the previous reported data, which is consistent with the results obtained here.
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Multiferroic materials are of particular interest due to the coexistence of ferromagnetic and ferroelectric properties. Among various multiferroics, bismuth iron oxide (BiFeO 3 , BFO) is the only material that shows both ferroelectric and... more
Multiferroic materials are of particular interest due to the coexistence of ferromagnetic and ferroelectric properties. Among various multiferroics, bismuth iron oxide (BiFeO 3 , BFO) is the only material that shows both ferroelectric and antiferromagnetic properties at room temperature. However, synthesis of phase pure BFO is difficult due to volatile nature of Bi 2 O 3. In this work, bismuth iron oxide nanoparticles are synthesized using sol-gel technique. With change in synthesis conditions a transition from amorphous nature to crystalline behavior is observed. The crystalline nature of nanoparticles strongly affects the dielectric and magnetic properties. High dielectric constant of ~300 (frequency =1kHz) is obtained due to presence of less conducting grain boundaries. Ferromagnetic behavior, instead of antiferromagnetic bismuth iron oxide, arises due to suppression of spiral spin structure of bismuth iron oxide.
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Iron oxides are material of interest because of their use in spintronic devices including Magnetic Tunnel Junctions (MTJ) and Random Access Memories (RAM). Among the various phases of iron oxide, Fe 2 O 3 is the most stable form which... more
Iron oxides are material of interest because of their use in spintronic devices including Magnetic Tunnel Junctions (MTJ) and Random Access Memories (RAM). Among the various phases of iron oxide, Fe 2 O 3 is the most stable form which shows antiferromagnetic or weak ferromagnetic behavior at room temperature. In order to enhance magnetic properties of Fe 2 O 3 , we here report the structural and magnetic properties of aluminum (Al) doped Fe 2 O 3 thin films prepared using sol-gel method. Effect of aluminum doping on Fe 2 O 3 thin films have been given very little consideration in the past particularly the reports on magnetic properties are limited. The presence of (012), (110), (006), (202), (024), (214) and (217) planes indicate the formation of pure hematite phase. No peaks corresponding to aluminum or aluminum oxide are observed. The undoped hematite thin films show ferromagnetic behavior as opposed to antiferromagnetic nature of bulk hematite. In case of hematite, spins in the adjacent planes are ferromagnetically coupled whereas, antiferromagnetic coupling arises with the spins of the adjacent planes. Spin orbit coupling between the two adjacent planes give rise to uncompensated spins of Fe 3+ cations. Remarkable increase in magnetic moment is observed with the increase in dopant concentration.
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Gold nanoparticles, owing to their fascinating optical properties, are considered very attractive for detecting devices. Size, shape as well as surrounding environment may affect the sensing behavior of nanomaterial and thus the study of... more
Gold nanoparticles, owing to their fascinating optical properties, are considered very attractive for detecting devices. Size, shape as well as surrounding environment may affect the sensing behavior of nanomaterial and thus the study of such factors is of great importance. We investigatedthe gas sensing performance of colloidal gold nanoparticles of different sizes in carbon dioxide gaseous environment by measuring the optical behavior with and without gas. The citrate reduction method was adopted to synthesize gold nanoparticles; scanning electron microscopy was used for morphological studies while optical properties were determined by spectroscopic ellipsometery. We observed a size dependent decrease in the transmission spectra of colloidal gold nanoparticles in the presence gaseous environment.
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Conducting nanocomposites of polyaniline/maghemite (PANI/ᵞ-Fe 2 O 3) have successfully prepared with different weight percentages of ᵞ-Fe 2 O 3 (0-0.5 wt. %) by adopting chemical oxidation route at 5ºC. These nanocomposites were... more
Conducting nanocomposites of polyaniline/maghemite (PANI/ᵞ-Fe 2 O 3) have successfully prepared with different weight percentages of ᵞ-Fe 2 O 3 (0-0.5 wt. %) by adopting chemical oxidation route at 5ºC. These nanocomposites were characterized for their structure, morphology and dc electrical conductivity by fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and standard two point probe method respectively. It can be clearly seen that dispersion of ᵞ-Fe 2 O 3 has imparted good structural and conducting properties in PANI matrix. The percolation threshold for dc electrical conductivity was found at 0.3% filling of maghemite contents in PANI chains.
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Bismuth iron oxide belongs to the class of materials that exhibits simultaneous presence of ferromagnetic and ferroelectric properties. However, synthesis of phase pure bismuth iron oxide presents some difficulties due to volatile nature... more
Bismuth iron oxide belongs to the class of materials that exhibits simultaneous presence of ferromagnetic and ferroelectric properties. However, synthesis of phase pure bismuth iron oxide presents some difficulties due to volatile nature of bismuth oxide. In order to overcome this difficulty, bismuth iron oxide thin films are prepared with variation in Bi/Fe ratio as 0.9, 0.95, 1.0, 1.05, 1.10, 1.15 and 1.20. XRD results confirm the formation of phase pure bismuth iron oxide in Bi/Fe ratio 1.0-1.10, while contribution from bismuth rich phase is observed as Bi/Fe ratio is increased to 1.20. Dielectric constant and tangent loss decrease as frequency of applied field increases and become constant at high frequencies. Dispersion in dielectric constant can be explained on the basis of Koop's theory based on Maxwell Wagner two-layered model. According to this model, specimen is composed of two layers, grains and grain boundaries. Grains are more conducting as compared to grain boundaries. At low frequencies, role of grain boundaries dominates resulting in high dielectric constant. At high frequencies, the role of grains dominates as a result of which the dielectric constant decreases at high frequencies along with decrease in tangent loss at high frequencies. Films show high transmission in the visible and infrared region with band gap in the range of 2.42eV-2.54eV. High refractive index of the films indicates compact structure of the films.