Mixed ion–electron conductor Ag2Se is an n-type semiconductor owing to the intrinsic Se vacancies... more Mixed ion–electron conductor Ag2Se is an n-type semiconductor owing to the intrinsic Se vacancies. By reducing Se vacancies, Ag2Se has been demonstrated as a potential environment-friendly thermoelectric material for near room temperature application. In the present work, Al addition was found to be highly beneficial for improving the thermoelectric properties of Ag2Se. In Ag1.95Al0.05Se, a large enhancement in the charge carrier mobility (1127 cm2/V s) is witnessed due to the formation of Se-rich Ag2Se1.02 phase with improved grain connectivity through in situ formed AgAl phase. The synergetic effect of low carrier concentration and enhanced mobility in Al doped samples resulted in a high Seebeck coefficient and high electrical conductivity, leading to a high power factor of 3039 μW/m K2 at 300 K. The figure-of-merit of Ag1.95Al0.05Se was found to be 1.1 at 300 K i.e., 57% higher than for pure Ag2Se. The uni-leg device fabricated using Ag1.95Al0.05Se with electroplated Ni/Ag contacts showed a conversion efficiency of ∼3.2% for a temperature difference of 93 K, i.e., comparable to the best reported value for conventional bismuth telluride.
The combined structural and dielectric response of langasite, Ba3NbFe3Si2O14 shows unique tempera... more The combined structural and dielectric response of langasite, Ba3NbFe3Si2O14 shows unique temperature and frequency dependence, attributed to presence of distributed potential wells.
High temperature superconducting films of YBa{sub 2}Cu{sub 3}O(7-x) YBCO were grown on SrTiO{sub ... more High temperature superconducting films of YBa{sub 2}Cu{sub 3}O(7-x) YBCO were grown on SrTiO{sub 3}, LaA1O{sub 3}, and YSZ substrates using two techniques: excimer laser ablation with in situ annealing and co-evaporation of Y, Cu, and BaF2 with ex-situ annealing. Film thicknesses were typically 5000 A, with predominant c-axis alignment perpendicular to the substrate. Critical temperatures up to Tc(R=O)=90 K were achieved by both techniques. Ellipsometric measurements were taken in the range 1.6 to 4.3 eV using a variable angle spectroscopic ellipsometer. The complex dielectric function of the laser ablated films was reproducible from run to run, and was found to be within 10 percent of that previously reported for (001) oriented single crystals. A dielectric overlayer was observed in these films, with an index of refraction of approximately 1.55 and nearly zero absorption. For the laser ablated films the optical properties were essentially independent of substrate material. The magnitude of the dielectric function obtained for the co-evaported films was much lower than the value reported for single crystals, and was sample dependent.
Mixed ion–electron conductor Ag2Se is an n-type semiconductor owing to the intrinsic Se vacancies... more Mixed ion–electron conductor Ag2Se is an n-type semiconductor owing to the intrinsic Se vacancies. By reducing Se vacancies, Ag2Se has been demonstrated as a potential environment-friendly thermoelectric material for near room temperature application. In the present work, Al addition was found to be highly beneficial for improving the thermoelectric properties of Ag2Se. In Ag1.95Al0.05Se, a large enhancement in the charge carrier mobility (1127 cm2/V s) is witnessed due to the formation of Se-rich Ag2Se1.02 phase with improved grain connectivity through in situ formed AgAl phase. The synergetic effect of low carrier concentration and enhanced mobility in Al doped samples resulted in a high Seebeck coefficient and high electrical conductivity, leading to a high power factor of 3039 μW/m K2 at 300 K. The figure-of-merit of Ag1.95Al0.05Se was found to be 1.1 at 300 K i.e., 57% higher than for pure Ag2Se. The uni-leg device fabricated using Ag1.95Al0.05Se with electroplated Ni/Ag contacts showed a conversion efficiency of ∼3.2% for a temperature difference of 93 K, i.e., comparable to the best reported value for conventional bismuth telluride.
The combined structural and dielectric response of langasite, Ba3NbFe3Si2O14 shows unique tempera... more The combined structural and dielectric response of langasite, Ba3NbFe3Si2O14 shows unique temperature and frequency dependence, attributed to presence of distributed potential wells.
High temperature superconducting films of YBa{sub 2}Cu{sub 3}O(7-x) YBCO were grown on SrTiO{sub ... more High temperature superconducting films of YBa{sub 2}Cu{sub 3}O(7-x) YBCO were grown on SrTiO{sub 3}, LaA1O{sub 3}, and YSZ substrates using two techniques: excimer laser ablation with in situ annealing and co-evaporation of Y, Cu, and BaF2 with ex-situ annealing. Film thicknesses were typically 5000 A, with predominant c-axis alignment perpendicular to the substrate. Critical temperatures up to Tc(R=O)=90 K were achieved by both techniques. Ellipsometric measurements were taken in the range 1.6 to 4.3 eV using a variable angle spectroscopic ellipsometer. The complex dielectric function of the laser ablated films was reproducible from run to run, and was found to be within 10 percent of that previously reported for (001) oriented single crystals. A dielectric overlayer was observed in these films, with an index of refraction of approximately 1.55 and nearly zero absorption. For the laser ablated films the optical properties were essentially independent of substrate material. The magnitude of the dielectric function obtained for the co-evaported films was much lower than the value reported for single crystals, and was sample dependent.
Mixed ion–electron conductor Ag2Se is an n-type semiconductor owing to the intrinsic Se vacancies... more Mixed ion–electron conductor Ag2Se is an n-type semiconductor owing to the intrinsic Se vacancies. By reducing Se vacancies, Ag2Se has been demonstrated as a potential environment-friendly thermoelectric material for near room temperature application. In the present work, Al addition was found to be highly beneficial for improving the thermoelectric properties of Ag2Se. In Ag1.95Al0.05Se, a large enhancement in the charge carrier mobility (1127 cm2/V s) is witnessed due to the formation of Se-rich Ag2Se1.02 phase with improved grain connectivity through in situ formed AgAl phase. The synergetic effect of low carrier concentration and enhanced mobility in Al doped samples resulted in a high Seebeck coefficient and high electrical conductivity, leading to a high power factor of 3039 μW/m K2 at 300 K. The figure-of-merit of Ag1.95Al0.05Se was found to be 1.1 at 300 K i.e., 57% higher than for pure Ag2Se. The uni-leg device fabricated using Ag1.95Al0.05Se with electroplated Ni/Ag contacts showed a conversion efficiency of ∼3.2% for a temperature difference of 93 K, i.e., comparable to the best reported value for conventional bismuth telluride.
The combined structural and dielectric response of langasite, Ba3NbFe3Si2O14 shows unique tempera... more The combined structural and dielectric response of langasite, Ba3NbFe3Si2O14 shows unique temperature and frequency dependence, attributed to presence of distributed potential wells.
High temperature superconducting films of YBa{sub 2}Cu{sub 3}O(7-x) YBCO were grown on SrTiO{sub ... more High temperature superconducting films of YBa{sub 2}Cu{sub 3}O(7-x) YBCO were grown on SrTiO{sub 3}, LaA1O{sub 3}, and YSZ substrates using two techniques: excimer laser ablation with in situ annealing and co-evaporation of Y, Cu, and BaF2 with ex-situ annealing. Film thicknesses were typically 5000 A, with predominant c-axis alignment perpendicular to the substrate. Critical temperatures up to Tc(R=O)=90 K were achieved by both techniques. Ellipsometric measurements were taken in the range 1.6 to 4.3 eV using a variable angle spectroscopic ellipsometer. The complex dielectric function of the laser ablated films was reproducible from run to run, and was found to be within 10 percent of that previously reported for (001) oriented single crystals. A dielectric overlayer was observed in these films, with an index of refraction of approximately 1.55 and nearly zero absorption. For the laser ablated films the optical properties were essentially independent of substrate material. The magnitude of the dielectric function obtained for the co-evaported films was much lower than the value reported for single crystals, and was sample dependent.
Mixed ion–electron conductor Ag2Se is an n-type semiconductor owing to the intrinsic Se vacancies... more Mixed ion–electron conductor Ag2Se is an n-type semiconductor owing to the intrinsic Se vacancies. By reducing Se vacancies, Ag2Se has been demonstrated as a potential environment-friendly thermoelectric material for near room temperature application. In the present work, Al addition was found to be highly beneficial for improving the thermoelectric properties of Ag2Se. In Ag1.95Al0.05Se, a large enhancement in the charge carrier mobility (1127 cm2/V s) is witnessed due to the formation of Se-rich Ag2Se1.02 phase with improved grain connectivity through in situ formed AgAl phase. The synergetic effect of low carrier concentration and enhanced mobility in Al doped samples resulted in a high Seebeck coefficient and high electrical conductivity, leading to a high power factor of 3039 μW/m K2 at 300 K. The figure-of-merit of Ag1.95Al0.05Se was found to be 1.1 at 300 K i.e., 57% higher than for pure Ag2Se. The uni-leg device fabricated using Ag1.95Al0.05Se with electroplated Ni/Ag contacts showed a conversion efficiency of ∼3.2% for a temperature difference of 93 K, i.e., comparable to the best reported value for conventional bismuth telluride.
The combined structural and dielectric response of langasite, Ba3NbFe3Si2O14 shows unique tempera... more The combined structural and dielectric response of langasite, Ba3NbFe3Si2O14 shows unique temperature and frequency dependence, attributed to presence of distributed potential wells.
High temperature superconducting films of YBa{sub 2}Cu{sub 3}O(7-x) YBCO were grown on SrTiO{sub ... more High temperature superconducting films of YBa{sub 2}Cu{sub 3}O(7-x) YBCO were grown on SrTiO{sub 3}, LaA1O{sub 3}, and YSZ substrates using two techniques: excimer laser ablation with in situ annealing and co-evaporation of Y, Cu, and BaF2 with ex-situ annealing. Film thicknesses were typically 5000 A, with predominant c-axis alignment perpendicular to the substrate. Critical temperatures up to Tc(R=O)=90 K were achieved by both techniques. Ellipsometric measurements were taken in the range 1.6 to 4.3 eV using a variable angle spectroscopic ellipsometer. The complex dielectric function of the laser ablated films was reproducible from run to run, and was found to be within 10 percent of that previously reported for (001) oriented single crystals. A dielectric overlayer was observed in these films, with an index of refraction of approximately 1.55 and nearly zero absorption. For the laser ablated films the optical properties were essentially independent of substrate material. The magnitude of the dielectric function obtained for the co-evaported films was much lower than the value reported for single crystals, and was sample dependent.
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