Effect of La3+, Ag+ and Bi3+ doping on thermoelectric properties of SrTiO3: First-principles investigation

Abstract

First principles calculations were applied to study the thermoelectric properties of La3+-, Ag+- and Bi3+- doped SrTiO3. With the exception of Sr0.9La0.1TiO3, the band gaps of Sr0.8La0.1Ag0.1TiO3, Sr0.8La0.1Bi0.1TiO3 and Sr0.7La0.1Ag0.1Bi0.1TiO3 were higher than that of SrTiO3. La3+, Ag+, and Bi3+ doping can cause an increase in electrical conductivity and power factor, and a decrease in thermal conductivity, which improves the ZT. The thermal conductivities of SrTiO3, Sr0.9La0.1TiO3, Sr0.8La0.1Ag0.1TiO3, Sr0.8La0.1Bi0.1TiO3 and Sr0.7La0.1Ag0.1Bi0.1TiO3 successively decreased, while power factor and ZT increased. Sr0.7La0.1Ag0.1Bi0.1TiO3, in particular, has the smallest thermal conductivity (2.237 W/m/K), the highest power factor (1.18 mW/(mK2)) and ZT (0.597) at 1200 K, 2.195 times larger than that of SrTiO3 (0.272). In addition, the solid state reaction method was applied to prepare dense ceramics of 10 wt% Bi-doped and (Bi, Ag)-codoped Sr0.9La0.1TiO3. It is demonstrated that (Bi, Ag)-codoped Sr0.9La0.1TiO3 have improved power factors, thermal conductivities and ZT values. The calculations and experimental results are consistent. This work demonstrates a method of co-doping Bi3+, Ag+, and La3+ to enhance the thermoelectric performance of SrTiO3.