Tuning anisotropic thermoelectric properties of TiS2–δ compounds via intercalating iron

Layered TiS2 is of great potential in thermoelectrics for room temperature and medium temperature applications due to its tunable transport properties, low environmental impact, low cost, and lightweight. Herein, we prepared FexTiS2–δ with x varying from 0 to 0.05 through a two-step process, involving initial synthesis in sealed tubes followed by spark plasma sintering. Mössbauer spectroscopy indicated that Fe atoms occupy the octahedral sites in the van der Waals gaps and exist in the form of Fe2+ with a high spin state. FexTiS2–δ with x ≤ 0.02 exhibit high in-plane power factors, reaching an average of ∼ 1.2 mWm–1K–2. The structural disorder caused by Fe intercalation leads to a significant decrease in out-of-plane lattice thermal conductivity. The anisotropy in the figure of merit, ZT, of FexTiS2–δ is suppressed due to Fe intercalation. Fe0.01TiS2–δ possesses the highest ZT of 0.39 at 625 K along the in-plane direction.