Electrical And Thermal Transport Properties Of Ternary Chalcopyrite CuGaTe₂-based Thermoelectric Materials

Thermoelectric?TE?materials have received worldwide concern in the recent decades,and play an important role in meeting the contemporary environmental pollution and energy crisis.TE materials can realize the mutual transformation of electricity and heat energy,which have a wide range of applications.However,the commercialization of TE materials is limited by the relatively lower conversion efficiency so that it is important to improve the thermoelectric figure of merit.CuGaTe₂-based materials are non-toxic and environmentally friendly p-type thermoelectric materials in the mid-temperature region.In this paper,we study about the ternary chalcopyrite CuGaTe₂-based materials by first-principles study and experimental research.The main results are as follow:?1?The electronic structures calculated by different methods are analyzed.The band gap value calculated by MBJ+U method is close to the experimental value.From the DOS of CuGaTe₂,the substitution of Zn at Ga site have a minor effect on the band structure near the valance band maximum,and only adjust the carrier concentration.The electrical transport properties of CuGaTe₂ are calculated and the results show that the largest power factor could be obtained in high carrier concentration range and it is lager at 700K than 900K.?2?The calculated phonon structure and lattice thermal conductivity of CuGaTe₂show that the lattice thermal conductivity of CuGaTe₂ is mainly derived from phonon scattering.The minimum lattice thermal conductivity of CuGaTe₂ is 0.46 W m^-1 K^-1.The z T value of CuGaTe₂ is predicted.The results indicate that decreasing the lattice thermal conductivity can significantly increase z T value of CuGaTe₂.?3?The experimental study on CuGaTe₂-based thermoelectric materials are conducted.The best SPS sintering process of CuGaTe₂ is 773K-50Mpa.Cu_1-xAg_xGa Te₂solid solution is beneficial to improve the Seebeck coefficient and electrical conductivity and reduce the lattice thermal conductivity,so that z T value can be greatly improved,for example the maximum z T value of Cu_0.8Ag_0.2Ga Te₂ and Cu_0.7Ag_0.3Ga Te₂can reach 1.0 at 820K,which is 53%higher than that of pure CuGaTe₂??0.65?.Introducing Cu vacancy defects could increase the carrier concentration of CuGaTe₂and decrease the lattice thermal conductivity.The maximum z T value of Cu_0.94Ga Te₂can reach 0.7.