Thermoelectric properties of Te-doped ternary CuAgSe compounds
Abstract
The ternary selenide CuAgSe shows great potential as a new promising thermoelectric material due to its superior carrier mobility and low lattice thermal conductivity. In this study, we doped Te at Se-sites and systematically studied the effect of Te-doping on the thermoelectric properties of the low-temperature CuAgSe phase (β-CuAgSe). It is found that the Te doping limit in β-CuAgSe is around 0.15. The longitudinal resistivity and Hall resistivity measurements under a magnetic field suggest that Te-doping exerts little effect on the band structure and the low-mobility carriers (holes) contribute weakly to the electrical transport in all Te-doped samples. Thus, the p–n transition and accompanying abrupt Seebeck coefficient decrease at elevated temperatures, which are quite common in non-stoichiometric β-CuAgSe samples, were not observed in Te-doped samples. Although the electrical conductivity of Te-doped samples is reduced due to the decreased carrier concentration and mobility, the significantly decreased thermal conductivity ensures that the Te-doped samples still maintain a similar or slightly higher thermoelectric figure of merit (zT) as compared with that of the stoichiometric β-CuAgSe. The maximum zT around 0.7 at 450 K is obtained in CuAgSe0.95Te0.05.
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