Reduction of working temperature for the large magnitude in thermoelectric dimensionless figure of merit of Ag_2−<i>x</i>Cu_<i>x</i>S

Abstract In this study, we try to reduce the temperature range for the large magnitude of dimensionless figure of merit ZT = 20 that was observed for the Ag 2 S composite consisting of low- and high-temperature phases under a unique temperature gradient at around 400 K. It reveals that partial substitution of Cu for Ag sites in Ag 2 S reduces the phase transition temperature, and subsequently the temperature range for this high ZT down to a temperature of 373 K. This result strongly suggests that our developed Cu-substituted Ag 2 S could be one of the best thermoelectric component materials in the generators capable of effectively recovering electric power from heat exchangers using hot water as a working liquid.