Large thermoelectric performance of heavily Nb-doped SrTiO3 epitaxial film at high temperature

Carrier concentration dependence of the thermoelectric figure of merit, $ZT$ of ${\mathrm{SrTiO}}_3$ at high-temperature (1000 K) is clarified using heavily Nb-doped ${\mathrm{SrTiO}}_3$ epitaxial films, which were grown on insulating (100)-oriented ${\mathrm{LaAlO}}_3$ single-crystalline substrates by a pulsed-laser deposition method. Carrier concentration, Hall mobility, Seebeck coefficient, and thermal conductivity of Nb-doped ${\mathrm{SrTiO}}_3$ epitaxial films were experimentally evaluated at 1000 K with an aid of theoretical analysis. $ZT$ of Nb-doped ${\mathrm{SrTiO}}_3$ increases with Nb concentration and it reaches $\sim 0.37$ (20% Nb doped), which is the largest value among $n$ -type oxide semiconductors ever reported.