Effects of Sintering Temperature on Thermoelectric Device of La-Doped Strontium Titanate in the Combination of Combustion Synthesis and Spark Plasma Sintering

Abstract

Thermoelectric properties of La-doped SrTiO₃ were investigated in order to determine the optimum sintering temperature for its fabrication by using a combination of combustion synthesis and spark plasma sintering. Combustion-synthesized samples (Sr_1−xLa_xTiO₃, x=0.08) were subjected to spark plasma sintering at temperatures from 1513 to 1663 K. The average grain size of sintered Sr_0.92La_0.08TiO₃ enlarged as sintering temperature rose up. The maximum average grain size was 23.5 μm for a sintering temperature of 1663 K. The thermoelectric properties of sintered Sr_0.92La_0.08TiO₃ were measured from room temperature to 1073 K. The optimum sintering temperature in the experimental sintering temperature range was 1633 K. Among the samples, the Sr_0.92La_0.08TiO₃ sample sintered at 1633 K showed the maximum power factor of 1.51×10⁻³ Wm⁻¹K⁻¹ at 375 K. Further, we investigated the effects of pressing direction during sintering on the thermoelectric properties of combustion-synthesized Sr_0.92La_0.08TiO₃. The combustion-synthesized samples were sintered well along the pressing direction during sintering; therefore, the electric conductivity measured along the pressing direction during sintering was more than twice that measured along the direction perpendicular to the pressing direction during sintering. Thus, we concluded that pressing direction during sintering affected the electric property of Sr_0.92La_0.08TiO₃.