Investigation of the Influence of Singly and Dually Doping Effect on Scattering Mechanisms and Thermoelectric Properties of Perovskite-Type STO

Abstract

This paper presents a systematic investigation of typical characterizations of Sr(_1-1.5x-0.5y)Dy_xTi_1-yNb_yO₃ composition based on single Nb- and Dy-doped as well as Nb/Dy co-doped SrTiO3. Nb concentration of 10, 13, 17, 20 and 24 at% and Dy concentration of 4, 8, 10, and 13 at% were used for different doping compounds. XRD data was used to calculate the lattice constants. The limit of solubility of doped element in host lattice was determined based on the graph showing the dependence of lattice parameters on doping concentration. The thermoelectric properties were investigated from 20 to 1000°C or 293 to 1273 K. The electrical conductivity increases below 600 K but decreases above 600 K with increasing doping content for all cases. This characterization reached about 900 S/cm at 570 K with 4% dysprosium and 20% niobium doped in STO. Both the electrical and thermal conductivity of single Nb-doped samples increase with increasing Nb content. In contrast, the thermal conductivity of single Dy doping decreases with increasing Dy content and consequently best absolute values of Seebeck coefficient. Generally, increasing doping concentration provides larger magnitude of Seebeck coefficient for all cases of doping. The best magnitude of the figure of merit reaches approximately 0.17 at 1273 K. The optimized composition should comprise quaternary compounds of which is Sr_0.84Dy_0.04Ti_0.80Nb_0.2O₃, especially for fast cooling regime.