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 ( 10 1 ¯ )[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.