Effect of sintering temperature on thermoelectric properties of La-doped SrTiO 3 ceramics prepared by sol–gel process and spark plasma sintering

Abstract

Single-phase polycrystalline La 0.08Sr 0.92TiO 3 ceramics were prepared by spark plasma sintering (SPS) using sol–gel-derived powders. The La 0.08Sr 0.92TiO 3 bulks had highly relative density (∼92%), and the grain size of the samples obviously grew from 300 nm to 3 μm when the SPS temperature increased from 1203 to 1473 K. The electrical conductivity increased with SPS-processing temperature owing to the increase of relative density, grain size, and oxygen vacancies due to the reducing atmosphere of SPS. The absolute value of Seebeck coefficient increased as the SPS temperature increased from 1203 to 1373 K, and then decreased by further increasing SPS temperature to 1473 K. The sample SPSed at 1373 K had the largest absolute value of Seebeck coefficient of 196 μVK −1 at 679 K. Sol–gel process and SPS can significantly decrease the thermal conductivity of SrTiO 3 based ceramics, whose lowest value was reduced to 1.19 Wm −1k −1 at 773 K in the sample SPSed at 1203 K. The maximum ZT value of 0.08 was obtained at 679 K for the sample SPSed at 1473 K.