Effects of AgSnSe₂ addition on the thermoelectric properties of Bi_0.5Sb_1.5Te₃

In this study, the thermoelectric properties of Bi_0.5Sb_1.5Te₃ with the addition of AgSnSe₂ were investigated. It was found that the addition of AgSnSe₂ significantly improved the electrical conductivity of the Bi_0.5Sb_1.5Te₃ based sample, which was attributed to the spontaneous Ag doping and the generation of the high carrier concentration SnTe secondary phase. Due to the significant increase in σ, the maximum PF increased to ∼39 μW cm⁻¹K⁻² at 323 K. Meanwhile, owing to the larger lattice anharmonicity by spontaneous Ag doping and enhanced interfacial scattering of phonons by secondary phase SnTe, κ_l decreases from 1.17 W m⁻¹ K⁻¹ for the intrinsic sample to 0.72 W m⁻¹ K⁻¹ for the x = 0.5 sample at 300 K. Thanks to the synergistic effect of AgSnSe₂ addition, a larger ZT of 1.1 at 373 K is obtained in Bi_0.5Sb_1.5Te₃-0.4% AgSnSe₂, which is 1.45 times higher than that of the intrinsic sample.