Anisotropic multicenter bonding and high thermoelectric performance in electron-poor CdSb

Abstract

Long-standing challenges to simultaneously accomplish crystal-like electrical transport and glass-like thermal transport in materials hinder the development of thermoelectric energy conversion technologies. We show that the unusual combination of these transport properties can be realized in electron-poor II−V semiconductor CdSb. Anisotropic multicenter bonding in CdSb is essential to both electrical and thermal transport. The electrondeficiency-sharing multicenter interactions lead to low overall ionicity and hence relatively high carrier weighted mobility and power factor. The bond anisotropy causes large lattice anharmonicity, which coupled with low cutoff frequency of the longitudinal acoustic branch and low sound velocity, gives rise to intrinsically low lattice thermal conductivity, approaching the glass-limit at elevated temperatures. A maximum thermoelectric figure of merit ZT of ∼1.3 at 560 K and an average ZT of 1.0 between 300 K and 600 K are achieved for the 0.5 at. % Ag-doped sample, which makes CdSb an attractive candidate for low-intermediate temperature or multistage power generations. Our study advocates the search for high efficiency thermoelectric materials in compounds with anisotropic two- and multicenter bonding.