Stabilizing Distorted Ductile Semiconductors for Excellent Ductility and Thermoelectric Performance

Abstract

Element doping/alloying is a common strategy to tune the electrical and thermal transports of thermoelectric (TE) materials, but the doping/alloying limit of foreign elements in many TE materials is usually very low, bringing a great challenge to improve the TE performance. In this work, beyond the classic principle of “like dissolves like,” it is found that choosing the compound with a severely distorted lattice and diversified chemical bonding as the matrix also facilitates achieving a high doping/alloying limit. Taking ductile semiconductors as an example, this work shows that gold (Au) element is nearly immiscible in Ag₂S and Ag₂Te, but has a relatively high alloying limit in complex Ag₂S_0.5Te_0.5 meta-phase. Au in Ag₂S_0.5Te_0.5 significantly decreases the carrier concentration and improves the TE performance, but scarcely changes the mechanical properties. Consequently, Ag_1.99Au_0.01S_0.5Te_0.5 demonstrates both a high figure-or-merit of 0.95 at 550 K and extraordinary room-temperature ductility. This work offers an effective and general strategy to develop stabilized doped/alloyed TE materials.