A comparative study of thermoelectric Cu2TrTi3S8 (Tr = Co and Sc) thiospinels: Enhanced Seebeck coefficient via electronic structure modification

We studied the electronic structures of Cu2TryTi4–yS8 (Tr = Sc, Co) thiospinels by combining thermoelectric measurements and first-principles calculations. The showed n-type metallic properties governed a conductive network composed edge-shared (Ti/Tr)S6 octahedra. substitutions Sc Co for Ti decreased electron carrier concentration in similar manner, leading to increases both electrical resistivity Seebeck coefficient. Although was equivalent Tr Co, coefficient remarkably enhanced as compared that Sc. Co-substituted system ascribed increased density states conduction band near Fermi level due partial replacement Ti-3d orbitals Co-3d orbitals. Owing structure modification, higher dimensionless figure merit (ZT 0.2 at y 1–1.5) achieved samples 673 K.