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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 electron-deficiency-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 similar to 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.
