Published online by Cambridge University Press: 01 February 2011
We have studied the thermoelectric properties of thallium compounds as novel thermoelectric materials. Especially, we focus on the Ag-Tl-Te ternary system, in which we found that Ag9TlTe5 exhibits an excellent thermoelectric figure of merit (ZT= 1.23) because of its extremely low thermal conductivity (around 0.22 Wm−1K−1). In this paper, we studied the thermal conductivity of four kinds of ternary silver thallium tellurides: AgTl3Te2, AgTlTe, Ag8Tl2Te5 and Ag9TlTe5, for which we found room temperature values of 0.39, 0.26, 0.14 and 0.21 Wm−1K−1, respectively. In order to understand the extremely low thermal conductivity, we performed an ultrasonic pulse echo measurement and evaluated some thermophysical properties.