Hopping carrier mobilities and thermoelectric properties of oxide materials with perovskite-related structure

Thermoelectric properties of perovskite-type oxides are investigated with particular interests in their hopping carrier mobility. A series of partial substitution for metal cations in CaMnO₃, a perovskite-type oxide showing small polaron hopping conduction, reveals that larger substituents for both Ca and Mn sites result in higher carrier mobilities. Consequently, Bi and In attain the largest ZT values for the Ca and Mn site substitutions, respectively. Increase in the hopping intersite distance is suggested as a reason of the enhanced mobilities. As a consequence, the largest substituent for the Mn site, In, gives the highest mobility, and thereby brings about the largest power factor for Ca(Mn_0.9In_0.1)O₃. Also benefiting from the fairly low thermal conductivity, the In-substituted sample attains ZT = 0.16 at 900 °C.