Thermoelectrical properties of A-site substituted Ca1-xRexMnO3 system

CaMnO3 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 rho(rho(300 K)=2 Omega 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 rho. Structure and thermoelectric properties of polycrystalline samples Ca(1-x)A(x)MnO(3) (A=Yb, Tb, Nd, and Ho) have been investigated. Although rho strongly depends on the ionic radius < r(A)> and carrier concentration, we have shown that the thermal conductivity kappa is mainly driven by the atomic weight of the A site and decreases with it. Therefore, it seems that the S, rho, and kappa could be controlled separately. For instance, the highest dimensionless ZT (=0.16) has been obtained at 1000 K in the air for Ca0.9Yb0.1MnO3. (c) 2006 American Institute of Physics.