Effect of Cationic and Anionic Doping in the Quinary Zintl Phase Thermoelectric Material Ca5‐xYbxAl2‐yInySb6‐zSnz System

Abstract

Two dopants with quinary Zintl phases Ca1.02Yb3.98Al1.48In0.52Sb6 and Ca5Al1.73In0.27Sb5.44Sn0.56 were synthesized by arc melting followed by annealing to evaluate the possibility of exploiting them as p‐type thermoelectric materials. The phase purity and crystal structures were carefully determined by powder X‐ray diffraction and single‐crystal X‐ray diffraction analyses, and the refined isotypic Ca5Ga2Sb6‐type structures were described as an assembly of the one‐dimensional anionic frameworks and the space‐filling cationic sites. The newly added cationic Yb and anionic Sn showed specific site‐preferences, which was elucidated by either the size‐factor or the electronic‐factor criterion. Moreover, these dopings were closely related to the phase transition of Ca1.02Yb3.98Al1.48In0.52Sb6 and the possible increase in electrical transport property of Ca5Al1.73In0.27Sb5.44Sn0.56. In particular, the thorough study for band structure of the Sn‐doped compound proves that the increased band extrema and degeneracies in the valence band can increase Seebeck coefficients, and the introduced atomic mixtures can lower thermal conductivities by increasing phonon scattering of title compounds.