High-temperature Thermoelectric Properties of Ca_0.9Y_0.1Mn_1-xFe_xO₃ (0 ≤ x ≤ 0.25)

Polycrystalline compounds of Ca0.9Y0.1Mn1-x FexO3 for 0 ≤ x ≤ 0.25 were prepared by solid-state reaction, followed by spark plasma sintering process, and
their thermoelectric properties from 300 to 1200 K were systematically investigated in terms of Y and Fe co-doping at the Ca- and Mn-sites, respectively. Crystal structure refinement revealed that all the investigated samples have the O′-type orthorhombic structure, and the lattice parameters slightly increased with increasing Fe concentration, causing a crystal distortion. It was found that with increasing the content of Fe doping, the Seebeck coefficient of Ca0.9Y0.1Mn12xFexO3 tended to increase, while the tendency toward the electrical conductivity was more complicated. The highest power factor was found to be 2.1 9 10-4 W/mK2 at 1150 K for the sample with x = 0.05 after annealing at 1523 K for 24 h in air. Thermal conductivity of the Fe-doped samples showed a lower value than that of the x = 0 sample, and the highest dimensionless figure of merit, ZT was found to be improved about 20 % for the sample with x = 0.05 as compared to that of the x = 0 sample at 1150 K.