ICT2014 Abstracts

Cu₃SbSe₄-based compounds composed of earth-abundant elements have been found to exhibit high thermoelectric performance at medium temperature. High ZT values were achieved in previous researches via regulating carrier density and forming solid solutions, but further insight into the transport mechanism as well as some key material parameters seems to be inadequate. In this work we study the electrical and thermal transport properties of Sn-doped Cu₃SbSe₄ thermoelectric materials between 300 K and 673 K. It is found here that the single parabolic band model explains the electrical transport very well. Experimentally we determined the band gap using Seebeck coefficient and optical absorption edge results from the undoped sample, both of which gave a direct band gap ~0.29 eV. Density-of-state effective mass is found to be about 1.5 m_e for doped samples. The transport properties at 300 K suggested a break of degeneracy near valence band maximum that was not captured by previous band structure calculation. The maximum ZT ~ 0.70 is obtained at 673 K and the optimized carrier density is ~ 1.8×10²⁰ cm^-3. The potential of further improvement of ZT via material engineering is briefly discussed.