Thermoelectrical properties of A -site substituted Ca1-x Rex Mn O3 system

CaMn O3 is an electron-doped compound which belongs to the perovskite family. Despite its high Seebeck coefficient S value, the figure of merit at high temperature remains low due to its large resistivity ρ (ρ 300 K =2 cm). To optimize the performance of this material in terms of thermoelectric properties, several substitutions have been attempted on the Ca site to decrease the ρ. Structure and thermoelectric properties of polycrystalline samples Ca1-x Ax Mn O3 (A=Yb, Tb, Nd, and Ho) have been investigated. Although ρ strongly depends on the ionic radius 〈rA〉 and carrier concentration, we have shown that the thermal conductivity κ is mainly driven by the atomic weight of the A site and decreases with it. Therefore, it seems that the S, ρ, and κ could be controlled separately. For instance, the highest dimensionless ZT (=0.16) has been obtained at 1000 K in the air for Ca0.9 Yb0.1 Mn O3.