Low-temperature structure and thermoelectric properties of ductile Ag2S0.4Te0.6

Abstract

Ductile Ag2S0.4Te0.6 shows promising thermoelectric properties and interesting phase transitions and structural features above room temperature. In this work, our experiments reveal that Ag2S0.4Te0.6 is composed of a Ag2Te-based glass and a Ag2S-based supercooled liquid at room temperature. The Ag2Te-based glass preserves its amorphous state in the measured temperature range (20–303 K), while the Ag2S-based supercooled liquid crystallizes into a triclinic phase below 183 K, leading to respectively the glass and crystalline-like thermal transport of Ag2S0.4Te0.6 near room temperature and at low temperature. At the crystallization point of the Ag2S-based phase, the electrical conductivity of Ag2S0.4Te0.6 shows an anomalous change. The extremely wide supercooling region (183–420 K) of the Ag2S-based phase leads to the unprecedented ductility of Ag2S0.4Te0.6. The thermoelectric figure of merit zT of Ag2S0.4Te0.6 increases monotonically with increasing temperature and reaches ∼0.17 at 300 K, showing the great potential as a ductile thermoelectric inorganic.