ICT2014 Abstracts

Lead telluride-based materials continue to be amongst the best thermoelectric materials for mid-to high-temperature power generation applications. However, concerns regarding lead toxicity have led us to consider alternate materials with properties similar to the lead-based compounds. The chalcopyrite semiconductor family consists of several compounds of general chemical formula I-III-VI2 or II-IV-V2, where the roman numerals indicate the respective elemental groups in the periodic table. This family spans a wide range of electronic band gaps (ranging from rougly 0.5 to 1.5 electronvolts), and previousstudies indicate thermoelectric figure of merit in excess of unity at 850K. Here we present results of our investigations of the thermoelectric properties of CuInTe2-CuGaTe2 solid solutions and solid solutions of zinc doped CuIn.99Zn.01Te2-CuGa.99Zn.01Te2.

Samples were synthesized by vacuum melting of stoichiometric ratios of the starting elements, followed by annealing. Sample purity was checked by x ray diffraction, and when verified the samples were ball milled in a high energy vibratory mill and hot pressed in an argon atmosphere. Final densities were measured by the Archimedes' method to assure sufficient densification. We observe a strong decrease in resistivity with the addition of Zn, indicating efficient p-type doping by this element, accompanied by an increase in thermoelectric power factor. This is verified by measurements of carrier concentration with a standard 5 probe hall measurement. Low temperature thermal conductivity was also slightly reduced with zinc doping, and substantially reduced with gallium substitutions, giving an increase in ZT at room temperature from both processes. High-temperature results show a ZT greater than 1 for multple samples in the series.