Large thermoelectric power factor in TiS2 crystal with nearly stoichiometric composition -: art. no. 241104

A TiS2 crystal with a layered structure was found to have a large, thermoelectric power factor. The in-plane power factor S-2/rho at 300 K is 37.1 muW/K-2 cm with resistivity (rho) of 1.7 mOmega cm and thermopower (S) of -251 muV/K, and this value is comparable to that of the best thermoelectric material, Bi2Te3 alloy. The electrical resistivity shows both metallic and highly anisotropic behaviors, suggesting that the electronic structure of this TiS2 crystal has a quasi-two-dimensional nature. The large thermoelectric response can be ascribed to the large density of states just above the Fermi energy and inter-valley scattering. In spite of the large power factor, the figure of merit ZT of TiS2 is 0.16 at 300 K, because of relatively large thermal conductivity, 68 mW/K cm. However, most of this value comes from reducible lattice contribution. Thus, ZT can be improved by reducing lattice thermal conductivity, e.g., by introducing a rattling unit into the inter-layer sites.