Microstructure and thermoelectric properties of Mg3(Bi,Sb)2 films containing a Mg metal phase

Abstract

Mg–Bi–Sb films with different Mg contents were prepared by magnetron sputtering on single-crystal Si(100) substrates containing 500 nm thick silicon oxide. The phase composition, chemical composition, surface and cross-sectional morphology, Seebeck coefficient, electrical conductivity, power factor, and density of states effective mass of the films were studied and analyzed. The results showed that the deposited Mg–Bi–Sb films consisted of a Mg₃(Bi,Sb)₂ solid solution and Mg metal phase. When the amount of Mg metal phase in the films increased, the room temperature carrier concentration, electrical conductivity and density of states effective mass increased, but the Seebeck coefficient and mobility decreased for the deposited Mg₃(Bi,Sb)₂ films with different Mg metal contents. In the studied range of Mg metal content (20.25 to 64.25 vol%), the power factor first increased and then decreased. Therefore, a small amount of Mg metal content in the Mg₃(Bi,Sb)₂ solid solution films improved the power factor. The standardized maximum power density (PD_max·L/ΔT²) of a thermoelectric generator based on the S2 film was 104.4 and 113.8 μW m⁻¹ K⁻² at temperature differences of ΔT = 35 K and 45 K.