Thermoelectric properties of Ca0.8Dy0.2MnO3 synthesized by solution combustion process

High-quality Ca0.8Dy0.2MnO3 nano-powders were synthesized by the solution combustion process. The size of the synthesized Ca0.8Dy0.2MnO3 powders was approximately 23 nm. The green pellets were sintered at 1150-1300°C at a step size of 50°C. Sintered Ca0.8Dy0.2MnO3 bodies crystallized in the perovskite structure with an orthorhombic symmetry. The sintering temperature did not affect the Seebeck coefficient, but significantly affected the electrical conductivity. The electrical conductivity of Ca0.8Dy0.2MnO3 increased with increasing temperature, indicating a semiconducting behavior. The absolute value of the Seebeck coefficient gradually increased with an increase in temperature. The highest power factor (3.7 × 10-5 Wm-1 K-2 at 800°C) was obtained for Ca0.8Dy0.2MnO3 sintered at 1,250°C. In this study, we investigated the microstructure and thermoelectric properties of Ca0.8Dy0.2MnO3, depending on sintering temperature

Impact of uniaxial strain and doping on oxygen diffusion in CeO2

Doped ceria is an important electrolyte for solid oxide fuel cell applications. Molecular dynamics simulations have been used to investigate the impact of uniaxial strain along the directions and rare-earth doping (Yb, Er, Ho, Dy, Gd, Sm, Nd, and La) on oxygen diffusion. We introduce a new potential model that is able to describe the thermal expansion and elastic properties of ceria to give excellent agreement with experimental data. We calculate the activation energy of oxygen migration in the temperature range 900-1900K for both unstrained and rare-earth doped ceria systems under tensile strain. Uniaxial strain has a considerable effect in lowering the activation energies of oxygen migration. A more pronounced increase in oxygen diffusivities is predicted at the lower end of the temperature range for all the dopants considered

Field-induced antiferroelectric-ferroelectric phase transitions in the Pb0.98La0.02(Zr0.70Hf0.30)(1-x)TixO3 system

Field-induced phase transitions of antiferroelectric-ferroelectric nature have been investigated in the Pb0.98La0.02(Zr0.70Hf0.30)(1-x)TixO3 system. Samples of compositions 0.065 less than or equal to x less than or equal to 0.10, located in the vicinity of an antiferroelectric-ferroelectric phase boundary, were analyzed by x-ray diffraction, by dielectric, and by electro-mechanical measurements. Samples with x less than or equal to 0.095 exhibited a metrically tetragonal structure, whereas the sample with x = 0.1 exhibited a rhombohedral structure. From the electromechanical measurements, the compositions deepest in the antiferroelectric phase field (x less than or equal to 0.075), were initially located in the antiferroelectric phase field (AFE(I)). The samples showed a pure electrostrictive behavior at low electric fields but underwent a phase transition into another antiferroelectric phase AFE(II) when submitted to higher electric fields. For intermediate compositions with 0.0775 less than or equal to x less than or equal to 0.095, the electric field enforced a transition between the antiferroelectric AFE(II) phase and the ferroelectric phase. In the latter compositional range, remanent ferroelectric behavior was detected at zero field and increased with Ti content until the ferroelectric phase remained metastable, in analogy with the better studied PbNbZrSnTiO3 and PbLaZrSnTiO3 systems. (C) 2000 American Institute of Physics. [S0021-8979(00)08003-8]