Structure and thermoelectric properties of 2D Cr₂Se_{3-3: X}S_{3 x} solid solutions

Chromium selenide (Cr₂Se₃), consisting of earth-abundant elements, is a new cost-efficient thermoelectric material. In this study, a series of Cr₂Se_3-3xS_3x (x = 0-0.1) solid solutions was synthesized by solid-state reaction combined with the spark plasma sintering (SPS) process. The correlation between sulphur substituted on selenium sites, the structure, and the thermoelectric properties of Cr₂Se_3-3xS_3x solid solutions was systematically investigated. The solubility limit of S in Cr₂Se_3-3xS_3x is about 10%. Through S substitutions, the band gap has been widened, the Seebeck coefficient has been effectively increased, and the lattice thermal conductivity has been substantially decreased. Mainly due to the remarkable decrease in the lattice thermal conductivity, the ZT values of Cr₂Se_3-3xS_3x (x = 0-0.1) solid solutions have been increased. The maximum ZT value of 0.29 has been achieved at 623 K for the Cr₂Se_2.7S_0.3 compound, which is 32% higher than the ZT value of pure Cr₂Se₃.