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.