Layer-Structured Metal Sulfides as Novel Thermoelectric Materials

Based on the above idea, we intercalate a layer of MS (M = Pb, Bi, Sn) into the van der Waals gap of layered TiS2, forming a series of misfit layer compounds (MS)1+x(TiS2)^2.3-5 They consist of an alternative stacking of CdI2-type TiS2 trigonal antiprismatic layers and rock-salt-type MS slabs, which could be viewed as a natural superlattice.6 The TiS2 layer can provide thermopower as well as electron pathway according to Imai’s research on TiS2 single crystal.⁷ The MS layer was intercalated into the gap of the TiS2 layers to form a modulated structure which would suppress the transport of phonons by the interaction between the MS layer and TiS2 layer and/or disruption of the periodicity of TiS2 in the direction perpendicular to the layers.