Composite perovskite-type ZnSnO3 improves the figure of merit and module efficiency of Bi0.4Sb1.6Te3 thermoelectrics

Abstract

Thermoelectric (TE) power generators provide an effective solution for recovering low-grade heat, driving the development of high-performance Bi₂Te₃ alloys. In this study, we enhanced the peak ZT to 1.43 at 350 K by incorporating perovskite-type ZnSnO₃ nanoparticles into Bi_0.4Sb_1.6Te₃, surpassing the performance of most (Bi,Sb)₂Te₃-based composites. The enhancement is attributed to the in-situ reaction between the decomposition products and the matrix, which optimizes hole concentration and enhances the density-of-states effective mass via the energy filtering effect, with minimal loss in hole mobility. Concurrently, microstructural evolution, including high-density twins and oxide nanoprecipitates, significantly reduces lattice thermal conductivity. These combined effects result in a 28 % improvement in the TE quality factor at 300 K, reaching 0.63 for the Bi_0.4Sb_1.6Te₃ + 0.4 wt% ZnSnO₃ sample. More significantly, when coupled with n-type zone-melted Bi₂Te_2.7Se_0.3, the well-designed 17-pair TE module achieves a conversion efficiency of 6.6 % under a 200 K temperature gradient, surpassing the majority of reported Bi₂Te₃-based modules, which further demonstrates the efficacy of the ZnSnO₃ compositing strategy and highlights the great potential for practical applications.