Phase Transition Behaviors and Thermoelectric Properties of CuAgTe_1-Se near 400 K

Phase transition is an effective strategy to engineer thermal conductivity and electrical transports. Recently, p-type CuAgTe_1-Se materials were reported to show excellent thermoelectric performance at 300-450 K, but the data are controversial due to the cooccurrence of phase transition in this temperature range. Accurately measuring and analyzing the electrical and thermal transport properties in the narrow phase transition temperature range is a quite challenging task. In this work, we systemically investigate the phase transition behavior, and electrical and thermal transport properties of p-type CuAgTe_1-Se (x = 0.3, 0.4, and 0.5) near 400 K. CuAgTe_1-Se (x = 0.3, 0.4, and 0.5) materials show similar phase transition temperatures but quite different phase transition speeds. The phase transition has a weak influence on the electrical transport properties of CuAgTe_0.7Se_0.3 and CuAgTe_0.6Se_0.4, but a strong influence on those of CuAgTe_0.5Se_0.5. Likewise, an obvious underestimation of thermal diffusivity, with a maximum deviation about 20% off the real value, is observed during the phase transition temperature range for CuAgTe_1-Se. Finally, CuAgTe_0.7Se_0.3 shows a peak zT around 0.9 at 390 K. The present study proves that CuAgTe_1-Se solid solutions are one kind of promising near-room-temperature thermoelectric material.