Thermal Stability and Electrical Transport Properties of Single-Crystalline β-Zn₄Sb₃ Co-doped by Ga/Sn

Abstract

In this study, Ga/Sn co-doped single-crystal β-Zn₄Sb₃ were prepared by a Sn-flux method based on stoichiometric ratios of Zn_4−x Sb₃Ga _x Sn₃ (x = 0, 0.25, 0.5, 0.6 and 0.75). The effect of Ga/Sn co-doping on the thermal stability and electrical transport properties of the obtained samples were investigated. All the prepared samples exhibit p-type conduction, and carrier concentration varies from 4.71 × 10¹⁹ cm⁻³ to 10.44 × 10¹⁹ cm⁻³, while carrier mobility changes from 34.2 cm² V⁻¹ s⁻¹ to 68.9 cm² V⁻¹ s⁻¹ at room temperature. Structure analysis indicates that all samples are β-Zn₄Sb₃ with space group $R\bar{3}c$. Thermal analysis results show that the Ga/Sn co-doped samples possess an excellent thermal stability. The results of crystal compositions indicate that both Ga and Sn atoms tend to replace Zn atoms, and the electrical transport properties of the samples were optimized by co-doping Ga and Sn. Meanwhile, the calculated values of the carrier effective mass, band gap and relaxation time agree with the result obtained from a band structure calculation. Consequently, the sample with Ga initial content x = 0.5 possesses excellent electrical properties, which obtains a maximal power factor of 1.56 × 10⁻³ W m⁻¹ K⁻² at 450 K.