Thermoelectric properties of CaMnO3 system

Ca
_1-x
RE
_x
MnO
₃
(RE: Nd, Tb, Ho, Yb, Lu, x = 0.1 and 0.2) bulks were prepared by a solid state reaction. They show metallic behavior at temperatures higher than about 400 K and electrical resistivity rho is lower than 12 mOmega cm at 1000 K in air. Absolute values of Seebeck coefficient S increases with temperature up to 973 K for all samples except Ca
_0.9
Yb
_0.1
MnO
₃
at 973 K. For Ca
_0.9
Lu
_0.1
MnO
₃
, S value reaches -130 muV/K at 973 K. Both thermoelectric properties are dominated mainly by crystallographic structure. Power factor PF (=S
²
/rho) increases with decreasing cell volume. Thermal conductivity kappa of Yb- and Lu-substituted samples is as low as 1.5 W/m-K
²
and dimension-less figure of merit ZT reaches 0.16 at 973 K for Ca
_0.8
Lu
_0.2
MnO
₃
in air.