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Papers by PRABHAKAR SINGH
Applied Physics Letters, 1986
We present the first theoretical study of the electronic properties of superlattices formed from ... more We present the first theoretical study of the electronic properties of superlattices formed from semimagnetic semiconductors. We explicitly consider the Cd0.8Mn0.2Te/Cd0.7Mn0.3Te superlattice system. We show magnetic field splittings both including (zero spin temperature) and neglecting (high spin temperature) the exchange interaction. We find that the exchange interaction dominates the magnetic effects. We present calculations of the derivative of the superlattice band gap with magnetic field as a function of the superlattice layer thickness. We show calculations of the change in superlattice band gap with magnetic field for several magnetic fields as a function of temperature.
Materials Science and Engineering: R: Reports, 2015
Judicious selection of mixed ionic-electronic conducting (MIEC) perovskite oxide as oxygen transp... more Judicious selection of mixed ionic-electronic conducting (MIEC) perovskite oxide as oxygen transport membrane (OTM) offers the potential to enhance overall process economics and systems performance for a wide variety of industrial applications ranging from clean and efficient energy conversion (oxy-combustion) to selective gas separation (high purity oxygen production) and value added chemicals (syngas and liquid fuel) production with near-zero greenhouse gas emissions. Doped lanthanum chromite perovskites have been considered as promising material of choice for oxygen transport membrane (OTM) due to their superior thermo-chemical stability in aggressive environment (800-1000°C, 0.21-10-20) than the other mixed ionic-electronic conducting (MIEC) perovskites such as ferrites and cobaltite's. Thermo-physical properties of the lanthanum chromite, required for optimum oxygen transport can be tuned by modifying the crystal structure, chemical
Journal of the American Ceramic Society, 2007
Exposure of (La0.90Sr0.10)0.98MnO3+δ (LSM‐10) to repeated oxygen partial pressure cycles (air/10 ... more Exposure of (La0.90Sr0.10)0.98MnO3+δ (LSM‐10) to repeated oxygen partial pressure cycles (air/10 ppm O2) resulted in enhanced densification rates, similar to behavior shown previously due to thermal cycling. Shrinkage rates in the temperature range 700°–1000°C were orders of magnitude higher than Makipirtti–Meng model estimations based on stepwise isothermal dilatometry results at a high temperature. A maximum in enhanced shrinkage due to oxygen partial pressure cycling occurred at 900°C. Shrinkage was the greatest when LSM‐10 bars that were first equilibrated in air were exposed to gas flows of lower oxygen fugacity than in the reverse direction. The former creates transient cation and oxygen vacancies well above the equilibrium concentration, resulting in enhanced mobility. These vacancies annihilate as Schottky equilibria are reestablished, whereas the latter condition does not lead to excess vacancy concentrations.
Applied Physics Letters, 1986
We present the first theoretical study of the electronic properties of superlattices formed from ... more We present the first theoretical study of the electronic properties of superlattices formed from semimagnetic semiconductors. We explicitly consider the Cd0.8Mn0.2Te/Cd0.7Mn0.3Te superlattice system. We show magnetic field splittings both including (zero spin temperature) and neglecting (high spin temperature) the exchange interaction. We find that the exchange interaction dominates the magnetic effects. We present calculations of the derivative of the superlattice band gap with magnetic field as a function of the superlattice layer thickness. We show calculations of the change in superlattice band gap with magnetic field for several magnetic fields as a function of temperature.
Materials Science and Engineering: R: Reports, 2015
Judicious selection of mixed ionic-electronic conducting (MIEC) perovskite oxide as oxygen transp... more Judicious selection of mixed ionic-electronic conducting (MIEC) perovskite oxide as oxygen transport membrane (OTM) offers the potential to enhance overall process economics and systems performance for a wide variety of industrial applications ranging from clean and efficient energy conversion (oxy-combustion) to selective gas separation (high purity oxygen production) and value added chemicals (syngas and liquid fuel) production with near-zero greenhouse gas emissions. Doped lanthanum chromite perovskites have been considered as promising material of choice for oxygen transport membrane (OTM) due to their superior thermo-chemical stability in aggressive environment (800-1000°C, 0.21-10-20) than the other mixed ionic-electronic conducting (MIEC) perovskites such as ferrites and cobaltite's. Thermo-physical properties of the lanthanum chromite, required for optimum oxygen transport can be tuned by modifying the crystal structure, chemical
Journal of the American Ceramic Society, 2007
Exposure of (La0.90Sr0.10)0.98MnO3+δ (LSM‐10) to repeated oxygen partial pressure cycles (air/10 ... more Exposure of (La0.90Sr0.10)0.98MnO3+δ (LSM‐10) to repeated oxygen partial pressure cycles (air/10 ppm O2) resulted in enhanced densification rates, similar to behavior shown previously due to thermal cycling. Shrinkage rates in the temperature range 700°–1000°C were orders of magnitude higher than Makipirtti–Meng model estimations based on stepwise isothermal dilatometry results at a high temperature. A maximum in enhanced shrinkage due to oxygen partial pressure cycling occurred at 900°C. Shrinkage was the greatest when LSM‐10 bars that were first equilibrated in air were exposed to gas flows of lower oxygen fugacity than in the reverse direction. The former creates transient cation and oxygen vacancies well above the equilibrium concentration, resulting in enhanced mobility. These vacancies annihilate as Schottky equilibria are reestablished, whereas the latter condition does not lead to excess vacancy concentrations.