High thermoelectric properties of Cu2TeAg2Te composite with Fe addition and non-stoichiometric Te

Cu 2 Te-based materials are a type of superionic conductor belonging to the class of phonon-liquid electron-crystal materials and have achieved high ZT values by doping and nanostructuring. However, it is easy to form copper vacancies in Cu 2 Te which leads to an excessive carrier concentration and then results in a low Seebeck coefficient. Hence, controlling copper ion migration and optimizing carrier concentration is essential to improve the thermoelectric performance of Cu 2 Te. This paper reports high-performance Cu 2 Te Ag 2 Te composite with high application value in the low-middle temperature region, which is achieved by fine tuning the carrier concentration using Fe addition and non-stoichiometric Te, as well as controlling the thermal conductivity of composite. A high ZT of ∼1.2 is obtained in AgCu 0.97 Fe 0.03 Te 0.96 at a low temperature of 573 K. Meanwhile, the phase transition mechanism of Cu 2 Te Ag 2 Te and its effect on the thermoelectric transport performance are revealed that go beyond nanostructuring and single-doping, which provides a strong theoretical basis for research and performance improvement of thermoelectric materials in this system.