Thermoelectric Properties of Rare Earth-doped SrTiO₃ Using Combination of Combustion Synthesis (CS) and Spark Plasma Sintering (SPS)

Abstract

Thermoelectric properties of combustion synthesized and spark plasma sintered rare-earth-doped (La, Sm, Gd, Dy and Y) SrTiO₃ was investigated from room temperature to 870 K from viewpoint of energy and time saving without deterioration in thermoelectric properties. All single phases of rare-earth-doped SrTiO₃ were successfully synthesized and sintered with high densities. With temperature increasing, the absolute value of Seebeck coefficient of all the samples increased and the electric conductivity decreased; the power factor of all the samples decreased except Y-doped sample in the considering temperature range. In all the samples, the La-doped sample and the Y-doped sample had the highest and lowest power factor, respectively. The figure of merit of La-doped samples with different doping amounts was evaluated and the maximum figure of merit 0.22 was obtained at 800 K from Sr_0.92La_0.08TiO₃ sample. Comparing Y and La-doped samples prepared by our synthesis method with that of conventional solid-state reaction method, the thermoelectric properties of our samples were relatively higher. Thus the combination of combustion synthesis and spark plasma sintering has a potential to prepare perovskite-oxide materials with relatively higher thermoelectric properties for high-temperature application.