Enhancement of Thermoelectric Performance of Sr0.9La0.1TiO3-Based Ceramics Regulated by Nanostructures

La-doped strontium titanite (Sr0.9La0.1TiO3) is a promising candidate for n-type oxide thermoelectric materials. However, the ZT values of this material are low, leading to low conversion efficiency. Improvements in this efficiency are required. In this work, a high ZT value of 0.50 was obtained for Sr0.9La0.1TiO3 ceramic samples by adding 10 wt % Bi2O3 sintering aids and 20 wt % nanosized Ti powders to the matrix material. Although Ti was oxidized to TiO2 during the sintering process, nanoscale phase interfaces were beneficial for phonon scattering and thermal conductivity reduction. Nanosized metallic Bi and Bi2O3 particles were observed. These two factors played an important role in reducing the thermal conductivity from 2.5 W/(m K) at room temperature to 1.31 W/(m K) at 1073 K. Nanostructure control using nanosized metal powders as additives combined with the Bi2O3 sintering aid paves a way for enhancement of thermoelectric properties of oxide thermoelectric materials.