Tuned thermoelectric properties of TiS1.5Se0.5 through copper intercalation

Polycrystalline samples of copper intercalated CuxTiS1.5Se0.5 (x = 0, 0.025, 0.05 and 0.1) are synthesized by classical high temperature reaction. The resulting powders are successfully densified by using spark plasma sintering. As expected, XRD refinements show that Cu intercalation between TiS1.5Se0.5 slabs induces an increase in the c lattice parameter. Electrical resistivity and Seebeck coefficient decrease drastically with increasing Cu content, direct consequence of the increased carrier concentration. In parallel, the lattice thermal conductivity of CuxTiS1.5Se0.5 is significantly reduced compared to unfilled TiS1.5Se0.5. Overall, the dimensionless thermoelectric figure of merit increases with temperature and reaches a maximum value of 0.54 at 700 K for Cu0.05TiS1.5Se0.5, the highest value so far observed in layered titanium chalcogenides.