Enhanced Thermoelectric Figure of Merit in Stannite–Kuramite Solid Solutions Cu2+xFe1–xSnS4–y (x = 0–1) with Anisotropy Lowering

In this Article, we elucidate the structural and thermoelectric properties of stannite-kuramite solid solutions, Cu(2+x)Fe(1-x)SnS(4-y) (x = 0-1), with sulfur defects (y) ≤ 0.4. Structural analysis revealed that anisotropy decreases and Cu/Sn disorder increases with an increase in x. The samples with x = 0.8-1 exhibit degenerate conduction, whereas the Seebeck coefficient (S) remains relatively high, S ≈ 100 μV K(-1) for x = 0.8 at 300 K. Thermal conductivities (κ) of the solid solutions are in the range 10(-3)-10(-2) W cm(-1) K(-1), which is close to the κ value of silicon dioxide. The dimensionless figure of merit (ZT) reaches 0.044 for x = 0.8 at 300 K. The ZT is enhanced significantly by an increase in temperature and is doubly larger than that of x = 0 at 300 K. These findings allow us to attain higher ZT values through optimization of chemical composition.