On the effects of substitution, intercalation, non-stoichiometry and block layer concept in TiS2 based thermoelectrics

TiS2 based layered sulfides have recently received increasing interest from the thermoelectric community. Due to its layered structure, the TiS2 compound with its enormous capacity for chemical substitution and intercalation offers different means to optimize the thermoelectric response through concomitant tuning of carrier concentration and decrease of the lattice thermal conductivity. In this review, we first discuss and summarize the crystal structures and physical/chemical properties of TiS2 based layered sulfides. Then, the approaches that successfully enhanced the thermoelectric performances in the TiS2 ceramic samples densified by Spark Plasma sintering are outlined, which include intercalation, non-stoichiometry, cationic substitution, and the block layer concept.