Effect of plastic deformation on phonon thermal conductivity of α -Ag2S

α-Ag2S is a ductile inorganic semiconductor recently identified, which can undergo considerable plastic deformation without the aid of dislocations. Together with its intrinsically poor electrical conductivity, it is one ideal system to study the effect of plastic deformation on phonon thermal transport. In this work, we show that the room temperature phonon thermal conductivity of α-Ag2S monotonically increases with compressive strain by about 32% at a compressive strain of 0.7. No deformation-induced phase transition occurs. Electrical conductivity and the Seebeck coefficient are basically invariant with deformation. No transport anisotropy is observed between the directions that are parallel and perpendicular to the compression direction. The stored energy in α-Ag2S measured by differential scanning calorimetry increases with strain but is remarkably larger than plastically deformed Cu at large strains. Possible origins for the increasing phonon thermal conductivity with plastic deformation are discussed. The present work provides original experimental observations on the effect of plastic deformation on phonon thermal conductivity, and it has important implications for the development of α-Ag2S-based ductile thermoelectric semiconductors and devices.