Ductile Ag₂₀ S₇ Te₃ with Excellent Shape-Conformability and High Thermoelectric Performance

Hetero-shaped thermoelectric (TE) generators (TEGs) can power the sensors used in safety monitoring systems of undersea oil pipelines, but their development is greatly limited by the lack of materials with both good shape-conformable ability and high TE performance. In this work, a new ductile inorganic TE material, Ag₂₀ S₇ Te₃ , with high TE performance is reported. At 300-600 K, Ag₂₀ S₇ Te₃ crystallizes in a body-centered cubic structure, in which S and Te atoms randomly occupy the (0, 0, 1) site. Due to the smaller generalized stacking fault energy in the ( $$ )[010] slip system, Ag₂₀ S₇ Te₃ shows better ductility than Ag₂ S, yielding excellent shape-conformability. The high carrier mobility and low lattice thermal conductivity observed in Ag₂₀ S₇ Te₃ result in a maximum dimensionless figure of merit (zT) of 0.80 at 600 K, which is comparable with the best commercial Bi₂ Te₃ -based alloys. The prototype TEG consisting of 10 Ag₂₀ S₇ Te₃ strips displays an open-circuit voltage of 69.2 mV and a maximum power output of 17.1 µW under the temperature difference of 70 K. This study creates a new route toward hetero-shaped TEG.