A2Cu3In3Te8 (A = Cd, Zn, Mn, Mg): A Type of Thermoelectric Material with Complex Diamond-like Structure and Low Lattice Thermal Conductivities

In this work, a type of thermoelectric chalcogenides A2Cu3In3Te8 (A = Cd, Zn, Mn, Mg), exhibiting intrinsically complex structures, low lattice thermal conductivities, high Seebeck coefficients, and thus promising thermoelectric properties, are designed and explored, by a systematic complex structure search surpassing the conventional doping and carrier concentration optimizing approach. The newly introduced alloying elements A (A= Cd, Zn, Mn, Mg) are found to uniformly distribute at the 4a and 4b sites which are solely occupied by Cu and In in cation sublattice of A2Cu3In3Te8, leading to the strong cation disordering but surprisingly stable phase. The cation disordering preserves the high structure symmetry and enhances the phonon scattering, leading to reasonably good electrical transport properties coexisting with extremely low lattice thermal conductivities (as low as ~0.32 W m-1 K-1 for Cd2Cu3In3Te8 at 873 K). A peak thermoelectric figure of merit zT ~0.9 at 873 K is achieved for Cd2Cu3In3Te8, which ...