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Dual occupations of sulfur induced band flattening and chemical bond softening in p-type SyCo4Sb12-2yS2y skutterudites
Journal of Materiomics  (IF6.425),  Pub Date : 2021-05-24, DOI: 10.1016/j.jmat.2021.05.003
Jialiang Li, Xiaolian Zhang, Haoqin Ma, Bo Duan, Guodong Li, Jiong Yang, Hongtao Wang, Houjiang Yang, Ling Zhou, Pengcheng Zhai

The electronegative filling in skutterudites not only broadened the scope of filling atoms, but also facilitated the preparation of p-type skutterudites. However, the introduction of a single sulfur atom in the Co4Sb12 cannot be achieved without charge compensation through the traditional equilibrium method. In the present study, the dual occupations of S-atoms by self-charge compensation were shown as the most stable forms under high pressure, and a series of p-type SyCo4Sb12−2yS2y skutterudites was successfully prepared by high-pressure-high-temperature (HPHT) method. The electronic structures and transport properties of as-obtained materials were investigated, and the related mechanisms were explored. The results suggested that the presence of S-impurities led to flattening of the electronic band that led to a higher Seebeck coefficient. The S-doped Co4Sb12 displayed lower elastic modulus, elastic constant, and Debye temperature, thus indicating the chemical bond softening in skutterudites. The thermal conductivities of SyCo4Sb12−2yS2y compounds reduced monotonously with the increase in S-content. This study provides a new and promising avenue for optimizing the thermoelectric properties of p-type Co4Sb12.