Preparation and thermoelectric properties of Co/Ni stabilized cubic Cu3SbS3 compounds

The anharmonicity of the lattice vibrations caused by 5s2 lone-pair electrons at Sb site has been considered to be the main reason for the low thermal conductivity of the compounds such as Cu3SbSe3, Cu3SbS3 and Cu12Sb4S13. In this study, by substituting Sb with Ni/Co without 5s2 lone-pair electrons, the cubic Cu3Sb1-x(Ni/Co)xS3 compounds were successfully synthesized by SPS and the effect of lone-pair electrons was further studied. The results demonstrate that both of the alloying effect and the change of valence bond environment of the Sb site caused by doping have a great influence on phonon transport. In addition, the increase of thermal conductivity caused by the latter is much greater than the inhibition of thermal conductivity by the former, which indicates the vital effect of the 5s2 lone-pair electrons on the decrease of thermal conductivity. When x= 0.05, the figure-of-merit zT values of the Ni and Co doped samples reach the maximum of 0.94 and 0.85 ​at 623 ​K, respectively, which are much higher than those of the undoped sample and the Fe doped samples, showing the potential of the Ni and Co doped compounds as high performance thermoelectric materials.