Enhancement of thermoelectric properties of SrTiO₃/LaNb-SrTiO₃ composite by different doping levels

Strontium titanate (STO) is an n-type oxide thermoelectric material, which has shown great prospects in recent years. The doping of La and Nb into STO can improve its power factor, whereas its thermal conductivity is still very high. Thus, in order to obtain a high thermoelectric figure-of-merit zT, it is very important to reduce its thermal conductivity. In this paper, using a combination of a hydrothermal method and a high-efficiency sintering method, we succeed in preparing a composite of pure STO and LaNb-doped STO, which simultaneously realizes lower thermal conductivity and higher Seebeck coefficient, therefore, the thermoelectric properties of STO are significantly improved. In the SrTiO₃/LaNb-SrTiO₃ bulk samples, the lowest thermal conductivity is 2.57 W·m^-1·K^-1 and the highest zT is 0.35 at 1000 K for the STO/La10Nb20-STO sample.