Enhanced Thermoelectric Performance of Nonstoichiometric Compounds Cu3-xSbSe4 by Cu Deficiencies

This work revealed that the Cu-deficient ternary compounds Cu 3-x SbSe 4 free of Te and Pb exhibit enhanced thermoelectric performance. Cu 3-x SbSe 4 (x = 0, 0.025, 0.050, 0.075) polycrystalline materials with high phase purity were fabricated by a facile method combining mechanical alloying and spark plasma sintering. Effects of Cu deficiencies on crystal structures, microstructures, element chemical states, and thermoelectric properties were systematically studied. High carrier concentration was obtained for the compositions Cu 2.95 SbSe 4 and Cu 2.925 SbSe 4 due to additional Cu vacancies, contributing to a remarkable increase in electrical conductivity. Together with a satisfactorily large Seebeck coefficient above 300 μV/K, a high power factor of about 890 μW/ m-K 2 at 523 K was achieved for Cu 2.95 SbSe 4 and Cu 2 . 925 SbSe 4 , almost 60% larger than that of the stoichiometric sample with x = 0. The maximum ZT value was increased to 0.50 at 673 K in the Cu 2.925 SbSe 4 sample sintered at a high temperature (703 K); this is the highest value reported so far for the undoped Cu 3 SbSe 4 system.