Nb-doped SrTiO3; n-type thermoelectric oxide with high ZT

[Appl. Phys. Lett. 2005/ J. Appl. Phys 2005/ J. Ceram. Soc. Japan 2006/ Appl. Phys. Lett. 2007/ J. Appl. Phys. 2007/ Phys. Rev. Lett. 2008 ]


The upper limit of thermoelectric figure of merit, ZT at high-temperature (1000 K) for heavily Nb-doped SrTiO3 is experimentally clarified using epitaxial films, which were grown on (100)-oriented LaAlO3 single-crystalline substrates at 700 oC by a pulsed-laser deposition method. Carrier concentration, Hall mobility, Seebeck coefficient and thermal conductivity of Nb-doped SrTiO3 epitaxial films were evaluated at 1000 K according to theoretical analysis. ZT of Nb-doped SrTiO3 increased with Nb-concentration, and it reached ~ 0.37 (20 % Nb-doped), which is the largest value among n-type oxide semiconductors ever reported.