Microstructure characterization and thermoelectric properties of Sr_0.9La_0.1TiO₃ ceramics with nano-sized Ag as additive

Sr_0.9La_0.1TiO₃ thermoelectric ceramics with different contents of nano-sized Ag metal particles as additive were prepared by conventional solid state reaction method, and the influences of Ag adding content on the microstructure and thermoelectric properties were investigated. XRD characterization confirmed that the main phase was perovskite Sr_0.9La_0.1TiO₃, along with a small amount of metal Ag phase. SEM images showed that all of the samples were dense, and the results of TEM indicated that the Ag particles accumulated at the grain boundaries to form a percolating network, contributing to increasing the electrical conductivity. Raman spectra of Sr_0.9La_0.1TiO₃/xAg samples before and after annealing in Ar+C atmosphere showed a great difference, resulting from the creation of oxygen vacancies and changes in the Ti–O bond vibration and rotation mode. With increasing Ag adding content, the absolute value of Seebeck coefficient increased. Ag addition caused an increase in carrier concentration and acted as electrical connections between the grains, which improved the electrical conductivity and reduced the thermal conductivity to 1.4–3.4 W/m/K. Finally, the maximum ZT value of ZT_883K = 0.30 was obtained for x = 20 wt% samples.