ICT2014 Abstracts

Binary chalcogenides such as Cu₂Se and Ag₂Sehave been found to exhibit superionic electrical conductivity at elevated temperatures, which makes them promising candidates to realize high thermoelectric figure of merit. A combination of these two alloys allows the charge carrier concentrations as well as their mobility to be varied and thus provides a method to tune the thermoelectric behavior. Hence in the present work, the two chalcogenides as well as their ternary alloys, Cu-Ag-Se, have been synthesized and investigated for high temperature thermoelectric application. The alloys have been synthesized from pure elements and their structural characterization performed using XRD and SEM. The elevated temperature up to 1000 K, thermoelectric properties - Seebeck coefficient, electrical conductivity and thermal conductivity of all the alloys has been studied in detail. The binary alloys Cu_1.98Se and Ag₂Se are essentially single phase and correspond to the low temperature α-phase. The ternary alloys,Cu_1.8Ag_0.2Se and Cu_1.58Ag_0.42Se on the other hand exhibit multiple phases corresponding to CuAgSe and Cu₂Se. The temperature dependence of thermal diffusivity indicates the presence of phase transitions in the alloys. The alloys Cu_1.98Se, Cu_1.8Ag_0.2Se and Cu_1.58Ag_0.42Se exhibit two distinct phase transitions while the Ag₂Se alloy exhibits a single phase transition. Also, the thermal diffusivity in all the alloys except Ag₂Se decreases with increasing temperature. All these results including the Seebeck coefficient and the electrical conductivity will be discussed in this work.