Simultaneous optimization of electrical and thermal transport properties of Bi0.5Sb1.5Te3 thermoelectric alloy by twin boundary engineering

• DOI: 10.1016/j.nanoen.2017.05.031
• Publication Date: 2017-05-14T13:45:44Z
• Authors: Yuan Yu; Dong-Sheng He; Siyuan Zhang; Oana Cojocaru-Mir...; Torsten Schwarz; Andreas Stoffers; Xiao-Yu Wang; Shuqi Zheng; Bin Zhu; Christina Scheu; Di Wu; Jia-Qing He; Matthias Wuttig; Zhong-Yue Huang; Fang-Qiu Zu
• Keywords: Spark Plasma Sintering; Melt spinning

Abstract The strong interdependence between the Seebeck coefficient, the electrical and thermal conductivity makes it difficult to obtain a high thermoelectric figure of merit, ZT . It is of critical significance to design a novel structure that manages to decouple these parameters. Here, we combine a liquid state manipulation method for solidified Bi 0.5 Sb 1.5 Te 3 alloy with subsequent melt spinning, ball milling, and spark plasma sintering processes, to construct dedicated microstructures containing plenty of 60° twin boundaries. These twin boundaries firstly scatter the very low-energy carriers and lead to an enhancement of the Seebeck coefficient. Secondly, they provide a considerable high carrier mobility, compensating the negative effect of the reduced hole concentration on the electrical conductivity. Thirdly, both experimental and calculated results demonstrate that the twin-boundary scattering dominates the conspicuous decrease of the lattice thermal conductivity. Consequently, the highest ZT value of 1.42 is achieved at 348 K, which is 27% higher than that of the sample with less twin boundary treated without liquid state manipulation. The average ZT value from 300 K to 400 K reaches 1.34. Our particular sample processing methods enabling the twin-dominant microstructure is an efficient avenue to simultaneously optimize the thermoelectric parameters.