Electron transport and thermoelectric response of Nb- or La-doped SrTiO3 epitaxial film at high-temperature

To clarify the potential of n-type conductive SrTiO₃ as a high temperature thermoelectric material, carrier concentration dependence of the thermoelectric figure of merit, ZT of SrTiO₃ at high-temperature (1000 K) is clarified using heavily Nb- or La-doped SrTiO₃ epitaxial films, which were grown on insulating (100)-oriented LaAlO₃ single-crystalline substrates by a pulsed-laser deposition method. Carrier concentration, Hall mobility, Seebeck coefficient and thermal conductivity of Nb- or La-doped SrTiO₃ epitaxial films were experimentally evaluated at 1000 K with an aid of theoretical analysis. The maximum ZT value was obtained ZT = 0.37 for 4 × 10²¹ cm^-3 Nb-doped SrTiO₃ at 1000 K, which is the largest value among n-type oxide semiconductors ever reported.