We present studies on the changes of the dielectric properties of 0.7 – 1.2-mm thick-layers of Sr... more We present studies on the changes of the dielectric properties of 0.7 – 1.2-mm thick-layers of Sr3Co2Fe24O41 Z-type hexaferrite in the frequency range 5 – 40 GHz; to the best of our knowledge, for the first time we used a combination of two methods – a resonance method, which yields infomation on the dielectric and magnetic anisotropies of the samples, and a broadband transmission-line method – covered coplanar and microstrip lines. We measured an increase of the dielectric constant and dielectric loss tangent above 20 GHz and a measurable anisotropy of the permittivity and permeability. The changes in the two parameters were also investigated (a magneto-electric effect was observed) in an external dc magnetic field in directions parallel and perpendicular to the sample at room temperature. The investigations presented are complex and intricate and should be considered as a first step in the characterization of thick Sr3Co2Fe24O41 Z-type hexaferrite slabs above 3 GHz up to the mm-wa...
Here, we report results on the magnetic and microwave properties of polycrystalline Y-type hexafe... more Here, we report results on the magnetic and microwave properties of polycrystalline Y-type hexaferrite synthesized by sol-gel auto-combustion and acting as a filler in a composite microwave-absorbing material. The reflection losses in the 1–20 GHz range of the Y-type hexaferrite powder dispersed homogeneously in a polymer matrix of silicon rubber were investigated in the absence and in the presence of a magnetic field. A permanent magnet was used with a strength of 1.4 T, with the magnetic force lines oriented perpendicularly to the direction of the electromagnetic wave propagation. In the case of using an external magnetic field, an extraordinary result was observed. The microwave reflection losses reached a maximum value of 35.4 dB at 5.6 GHz in the Ku-band without a magnetic field and a maximum value of 21.4 dB at 8.2 GHz with the external magnetic field applied. The sensitivity of the microwave properties of the composite material to the external magnetic field was manifested by...
2017 40th International Spring Seminar on Electronics Technology (ISSE), 2017
Ba<inf>2</inf>Mg<inf>2</inf>Fe<inf>12</inf>O<inf>22<... more Ba<inf>2</inf>Mg<inf>2</inf>Fe<inf>12</inf>O<inf>22</inf> is a Y-type hexagonal ferrite known for a relatively high temperature (∼200 K) of the magnetic transition to a spiral spin arrangement and an easy magnetization axis lying in a plane perpendicular to the c crystal axis. The multiferroicity exists in the absence of an external magnetic field H; a longitudinal-conical spin arrangement sets below 50 K; and the direction of the electric polarization P can be governed by relatively low magnetic fields (<0.02 T). The structural, magnetic and ferroelectric parameters have been mostly studied on monocrystals and, in spite of the attractive possibilities of designing promising composite multiferroic structures, the information on Ba<inf>2</inf>Mg<inf>2</inf>Fe<inf>12</inf>O<inf>22</inf>powders is scarce. We report on Ba<inf>2</inf>Mg<inf>2</inf>Fe<inf>12<...
In recent years, the Y-type hexaferrites have been the object of extensive research related to st... more In recent years, the Y-type hexaferrites have been the object of extensive research related to studying the magnetoelectric effect in the microwave frequency range that is typical for these materials and determines their potential use as microwave absorbers. The morphology of the investigated powders used as fillers in microwave absorbers considerably affects their properties. We present a study on the influence of the preparation technique on the morphology of Ba0.5Sr1.5Zn2Fe12O22 and Ba0.5Sr1.5Zn2Al0.08Fe11.92O22 powders. The powders were synthesized by acetic-acid sol-gel auto-combustion and ultrasonic co-precipitation. The particles of the samples obtained by ultrasonic co-precipitation had an almost perfect hexagonal shape typical for hexaferrites. Al-substitution in Ba0.5Sr1.5Zn2Fe12O22 (Ba0.5Sr1.5Zn2Al0.08Fe11.92O22) resulted in lowering the synthesis temperature.
2017 40th International Spring Seminar on Electronics Technology (ISSE), 2017
Ga-and In co-doped ZnO films have been successfully obtained by sol-gel approach. XRD analysis sh... more Ga-and In co-doped ZnO films have been successfully obtained by sol-gel approach. XRD analysis shows that Zn-In-Ga oxide films possess lower crystallinity compared with the undoped ZnO and ZnO:In films. The corresponding XRD lines are broader and less intense. FTIR detailed study of Zn-In-Ga oxides and ZnO shows that Ga and In codoping affects the shapes and the intensity of the absorption bands with no traces of Ga-O and In-O bonds. Optical study shows that the Zn-In-Ga oxide films have improved transparency compared to ZnO and ZnO:In films. The optical band gaps are estimated and discussed.
NATO Science for Peace and Security Series B: Physics and Biophysics, 2018
Ferrite materials suitable for mm-wave circulators should exhibit ferromagnetic resonance (FMR) i... more Ferrite materials suitable for mm-wave circulators should exhibit ferromagnetic resonance (FMR) in the mm range with high a saturation magnetization. In addition, the magnetic and dielectric losses and the temperature dependence of the magnetocrystalline anisotropy and of the saturation magnetization should be as low as possible. Therefore, compositionally and microstructurally homogeneous materials are required. The object of the work presented was to investigate the microwave (MW) absorbing properties of nanocomposite bulk samples. As a filler we used magnetite (Fe3O4) with different particle sizes in a silicone rubber matrix and investigated the influence of the filler concentration and particle size in the polymer matrix on the MW nonlinearity in a large frequency range (1–20 GHz). We found that the intensity and the frequency at the reflection loss minimum depend on the particle size and particle concentration of magnetite in the samples.
This work presents morphological, structural and optical studies of ZnO and ZnO:In nanostructured... more This work presents morphological, structural and optical studies of ZnO and ZnO:In nanostructured thin films depending on In doping (four different concentrations). XRD study of 600°C annealed ZnO:In films reveals that crystallization strongly depends on indium concentration. The films are crystallized in wurtzite structure and only for the films with highest In addition, two crystal phases are detected wurtzite ZnO and cubic In2O3. The AFM investigation reveals that the lowest Root Mean Squared Roughness(RMS) is revealed for ZnO:In 0.5 film (15.96 nm) and the roughness increases up to 64.52 nm for ZnO:In 1. Columnar type structures can be observed in the AFM micrographs of the other two films — ZnO:In 2 and ZnO:In 3, as the columns vary in height and size. The effect of the indium doping into ZnO reveals changing of optical transmittance compared to ZnO film. The optical band gap of ZnO:In films, annealed at 600°C is in the range of 3.06–3.27 eV.
The hexaferrites have been intensively investigated as materials for permanent magnets, high-dens... more The hexaferrites have been intensively investigated as materials for permanent magnets, high-density recording media, microwave devices, bio-medical applications and, recently, as multiferroic materials. It is well known that the electrical, optical and magnetic properties of materials vary widely with the particle size and shape and with the degree of crystallinity. In general, the technologies for preparation of hexaferrites require high-temperature annealing, which impedes the fabrication of nanosized hexaferrites characterized by a narrow particle-size distribution. The microemulsion method has been proposed precisely in order to overcome the difficulties related to controlling the size distribution of the particles of oxide materials and, especially, hexaferrites, since one of the advantages of this technique is the preparation of very uniform particles. The high homogeneity of the nanosized precipitate particles produced is due to the fact that each of the aqueous drops acts as a nanosized reactor for nanoparticles formation. The M-type hexaferrite is the most commonly studied member of the hexaferrite family. This review chapter will be focused on the synthesis and properties of hexaferrites (particularly nanosized hexaferrites) obtained by microemulsion. The different microemulsion systems will be presented and their influence on the structure and magnetic properties of the M-type hexaferrite will be discussed. A special emphasis will be placed on the preparation of hexaferrite powders with nanometer particle sizes via two approaches of the microemulsion technique, namely, single microemulsion and double microemulsion; original results will be presented.Peer reviewe
18th International School on Quantum Electronics: Laser Physics and Applications, 2015
Pulsed laser ablation was used to create Ag nanostructures – nanoparticles and nanowires. Two dif... more Pulsed laser ablation was used to create Ag nanostructures – nanoparticles and nanowires. Two different type of target motion were used – rotation and computer controlled by using an XY stage. The impact was investigated of the trajectory of the laser beam on the target surface on the characteristics of the ablation process itself and the nanostructures obtained. Two circular trajectories of different diameters generated at the target rotation were utilized. The fundamental (λ = 1064 nm) and the third harmonic (λTHG = 355 nm) wavelengths of a Nd-YAG laser system were used for the fabrication procedure. They were selected in order to study the influence of the two processes accompanying the ablation procedure, namely, scattering and absorption of the incident light by the nanostructures already created (the so-called self-absorption). The two possible nanostructures – nanoparticles and nanowires, were obtained by an appropriate choice of the laser fluence for each of the wavelengths selected. The optical extinction spectra of the fabricated colloids allowed an indirect assessment of the shape and size-distribution of the nanostructures obtained, whose size and morphology were visualized by transmission electron microscopy (TEM). It was established that the most appropriate processing conditions in terms of the efficiency of the ablation and reproducibility of the sample characteristics were achieved using a computer controlled XY stage.
We present studies on the changes of the dielectric properties of 0.7 – 1.2-mm thick-layers of Sr... more We present studies on the changes of the dielectric properties of 0.7 – 1.2-mm thick-layers of Sr3Co2Fe24O41 Z-type hexaferrite in the frequency range 5 – 40 GHz; to the best of our knowledge, for the first time we used a combination of two methods – a resonance method, which yields infomation on the dielectric and magnetic anisotropies of the samples, and a broadband transmission-line method – covered coplanar and microstrip lines. We measured an increase of the dielectric constant and dielectric loss tangent above 20 GHz and a measurable anisotropy of the permittivity and permeability. The changes in the two parameters were also investigated (a magneto-electric effect was observed) in an external dc magnetic field in directions parallel and perpendicular to the sample at room temperature. The investigations presented are complex and intricate and should be considered as a first step in the characterization of thick Sr3Co2Fe24O41 Z-type hexaferrite slabs above 3 GHz up to the mm-wa...
Here, we report results on the magnetic and microwave properties of polycrystalline Y-type hexafe... more Here, we report results on the magnetic and microwave properties of polycrystalline Y-type hexaferrite synthesized by sol-gel auto-combustion and acting as a filler in a composite microwave-absorbing material. The reflection losses in the 1–20 GHz range of the Y-type hexaferrite powder dispersed homogeneously in a polymer matrix of silicon rubber were investigated in the absence and in the presence of a magnetic field. A permanent magnet was used with a strength of 1.4 T, with the magnetic force lines oriented perpendicularly to the direction of the electromagnetic wave propagation. In the case of using an external magnetic field, an extraordinary result was observed. The microwave reflection losses reached a maximum value of 35.4 dB at 5.6 GHz in the Ku-band without a magnetic field and a maximum value of 21.4 dB at 8.2 GHz with the external magnetic field applied. The sensitivity of the microwave properties of the composite material to the external magnetic field was manifested by...
2017 40th International Spring Seminar on Electronics Technology (ISSE), 2017
Ba<inf>2</inf>Mg<inf>2</inf>Fe<inf>12</inf>O<inf>22<... more Ba<inf>2</inf>Mg<inf>2</inf>Fe<inf>12</inf>O<inf>22</inf> is a Y-type hexagonal ferrite known for a relatively high temperature (∼200 K) of the magnetic transition to a spiral spin arrangement and an easy magnetization axis lying in a plane perpendicular to the c crystal axis. The multiferroicity exists in the absence of an external magnetic field H; a longitudinal-conical spin arrangement sets below 50 K; and the direction of the electric polarization P can be governed by relatively low magnetic fields (<0.02 T). The structural, magnetic and ferroelectric parameters have been mostly studied on monocrystals and, in spite of the attractive possibilities of designing promising composite multiferroic structures, the information on Ba<inf>2</inf>Mg<inf>2</inf>Fe<inf>12</inf>O<inf>22</inf>powders is scarce. We report on Ba<inf>2</inf>Mg<inf>2</inf>Fe<inf>12<...
In recent years, the Y-type hexaferrites have been the object of extensive research related to st... more In recent years, the Y-type hexaferrites have been the object of extensive research related to studying the magnetoelectric effect in the microwave frequency range that is typical for these materials and determines their potential use as microwave absorbers. The morphology of the investigated powders used as fillers in microwave absorbers considerably affects their properties. We present a study on the influence of the preparation technique on the morphology of Ba0.5Sr1.5Zn2Fe12O22 and Ba0.5Sr1.5Zn2Al0.08Fe11.92O22 powders. The powders were synthesized by acetic-acid sol-gel auto-combustion and ultrasonic co-precipitation. The particles of the samples obtained by ultrasonic co-precipitation had an almost perfect hexagonal shape typical for hexaferrites. Al-substitution in Ba0.5Sr1.5Zn2Fe12O22 (Ba0.5Sr1.5Zn2Al0.08Fe11.92O22) resulted in lowering the synthesis temperature.
2017 40th International Spring Seminar on Electronics Technology (ISSE), 2017
Ga-and In co-doped ZnO films have been successfully obtained by sol-gel approach. XRD analysis sh... more Ga-and In co-doped ZnO films have been successfully obtained by sol-gel approach. XRD analysis shows that Zn-In-Ga oxide films possess lower crystallinity compared with the undoped ZnO and ZnO:In films. The corresponding XRD lines are broader and less intense. FTIR detailed study of Zn-In-Ga oxides and ZnO shows that Ga and In codoping affects the shapes and the intensity of the absorption bands with no traces of Ga-O and In-O bonds. Optical study shows that the Zn-In-Ga oxide films have improved transparency compared to ZnO and ZnO:In films. The optical band gaps are estimated and discussed.
NATO Science for Peace and Security Series B: Physics and Biophysics, 2018
Ferrite materials suitable for mm-wave circulators should exhibit ferromagnetic resonance (FMR) i... more Ferrite materials suitable for mm-wave circulators should exhibit ferromagnetic resonance (FMR) in the mm range with high a saturation magnetization. In addition, the magnetic and dielectric losses and the temperature dependence of the magnetocrystalline anisotropy and of the saturation magnetization should be as low as possible. Therefore, compositionally and microstructurally homogeneous materials are required. The object of the work presented was to investigate the microwave (MW) absorbing properties of nanocomposite bulk samples. As a filler we used magnetite (Fe3O4) with different particle sizes in a silicone rubber matrix and investigated the influence of the filler concentration and particle size in the polymer matrix on the MW nonlinearity in a large frequency range (1–20 GHz). We found that the intensity and the frequency at the reflection loss minimum depend on the particle size and particle concentration of magnetite in the samples.
This work presents morphological, structural and optical studies of ZnO and ZnO:In nanostructured... more This work presents morphological, structural and optical studies of ZnO and ZnO:In nanostructured thin films depending on In doping (four different concentrations). XRD study of 600°C annealed ZnO:In films reveals that crystallization strongly depends on indium concentration. The films are crystallized in wurtzite structure and only for the films with highest In addition, two crystal phases are detected wurtzite ZnO and cubic In2O3. The AFM investigation reveals that the lowest Root Mean Squared Roughness(RMS) is revealed for ZnO:In 0.5 film (15.96 nm) and the roughness increases up to 64.52 nm for ZnO:In 1. Columnar type structures can be observed in the AFM micrographs of the other two films — ZnO:In 2 and ZnO:In 3, as the columns vary in height and size. The effect of the indium doping into ZnO reveals changing of optical transmittance compared to ZnO film. The optical band gap of ZnO:In films, annealed at 600°C is in the range of 3.06–3.27 eV.
The hexaferrites have been intensively investigated as materials for permanent magnets, high-dens... more The hexaferrites have been intensively investigated as materials for permanent magnets, high-density recording media, microwave devices, bio-medical applications and, recently, as multiferroic materials. It is well known that the electrical, optical and magnetic properties of materials vary widely with the particle size and shape and with the degree of crystallinity. In general, the technologies for preparation of hexaferrites require high-temperature annealing, which impedes the fabrication of nanosized hexaferrites characterized by a narrow particle-size distribution. The microemulsion method has been proposed precisely in order to overcome the difficulties related to controlling the size distribution of the particles of oxide materials and, especially, hexaferrites, since one of the advantages of this technique is the preparation of very uniform particles. The high homogeneity of the nanosized precipitate particles produced is due to the fact that each of the aqueous drops acts as a nanosized reactor for nanoparticles formation. The M-type hexaferrite is the most commonly studied member of the hexaferrite family. This review chapter will be focused on the synthesis and properties of hexaferrites (particularly nanosized hexaferrites) obtained by microemulsion. The different microemulsion systems will be presented and their influence on the structure and magnetic properties of the M-type hexaferrite will be discussed. A special emphasis will be placed on the preparation of hexaferrite powders with nanometer particle sizes via two approaches of the microemulsion technique, namely, single microemulsion and double microemulsion; original results will be presented.Peer reviewe
18th International School on Quantum Electronics: Laser Physics and Applications, 2015
Pulsed laser ablation was used to create Ag nanostructures – nanoparticles and nanowires. Two dif... more Pulsed laser ablation was used to create Ag nanostructures – nanoparticles and nanowires. Two different type of target motion were used – rotation and computer controlled by using an XY stage. The impact was investigated of the trajectory of the laser beam on the target surface on the characteristics of the ablation process itself and the nanostructures obtained. Two circular trajectories of different diameters generated at the target rotation were utilized. The fundamental (λ = 1064 nm) and the third harmonic (λTHG = 355 nm) wavelengths of a Nd-YAG laser system were used for the fabrication procedure. They were selected in order to study the influence of the two processes accompanying the ablation procedure, namely, scattering and absorption of the incident light by the nanostructures already created (the so-called self-absorption). The two possible nanostructures – nanoparticles and nanowires, were obtained by an appropriate choice of the laser fluence for each of the wavelengths selected. The optical extinction spectra of the fabricated colloids allowed an indirect assessment of the shape and size-distribution of the nanostructures obtained, whose size and morphology were visualized by transmission electron microscopy (TEM). It was established that the most appropriate processing conditions in terms of the efficiency of the ablation and reproducibility of the sample characteristics were achieved using a computer controlled XY stage.
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