Improved densification and thermoelectric performance of In₅SnSbO₁₂ via Ga doping

In₅SnSbO₁₂ is being considered for use in thermoelectric applications. It has a satisfactory electrical conductivity and is expected to possess low thermal conductivity. However, it is difficult to densify In₅SnSbO₁₂ by conventional solid-state reaction method. In this work, we demonstrated that Ga doping could increase the relative density of In₅SnSbO₁₂, from ~ 60% (x = 0) to ~ 90% (x = 0.1). The improved densification may be attributable to the increased cationic occupancy after the addition of Ga and the reduced grain size induced by the presence of the secondary phase Ga₂In₆Sn₂O₁₆. The improved relative density led to a significant reduction in electrical resistivity; for example, for x = 0.1, the lowest electrical resistivity was ~ 0.002 Ω cm at 973 K, which was five times lower than that of the undoped sample (x = 0). The resultant power factor of this sample had a value of 3.4 × 10⁻⁴ Wm⁻¹ K⁻² at 973 K, which was nearly four times higher than that of the undoped sample. Although thermal conductivities were increased with Ga doping due to the enhanced densification, they were lower than that of In₂O₃. The highest thermoelectric performance was achieved in the sample with x = 0.05, specifically zT ~ 0.17 at 973 K. These results indicate that the addition of Ga to In₅SnSbO₁₂ results in a material which is more promising for thermoelectric applications.