Large thermoelectric response of metallic perovskites: Sr_1-xLa_xTiO₃ (0<~x<~0.1)

Thermoelectric properties have been investigated for single crystals of Sr_1-xLa_xTiO₃ for 0<~x<~0.1. We have found a large power factor (defined as PF=S²/ρ, S and ρ being the Seebeck coefficient and resistivity, respectively), 28-36 μW/(K² cm), at room temperature in the metallic region with carrier density (n) of (0.2-2)×10²¹ cm^-3. The observed PF is comparable to that of Bi₂Te₃ with much lower n (∼1×10¹⁹ cm^-3). Such an unexpectedly large PF or S at the metallic carrier density is ascribed to the orbital degeneracy (threefold) of the Ti 3d-t_2g conduction band and the relatively large effective mass of conduction electrons as well as to the large energy-dependent scattering rate.