Mo6Se8-based Chevrel phase thermoelectric materials

Mo₆Se₈-based Chevrel phase compounds inserted cations into those cavities are interesting as a new kind of PGEC (Phonon Glass Electron Crystal) thermoelectric materials. Ti and Zn are expected to form attractive Chevrel phase thermoelectric compounds by theoretical considerations. In our previous investigation, however, it seems to be difficult that cations insert sufficiently to cavities. In this study, an attempt to increase the amount of inserted Ti by varying preparation conditions is carried out. It is apparent that this trouble is caused by the formation of a TiSe₂ secondary phase due to preferential diffusion of Se into Ti, which consequently disturbed the reaction of Mo and Se. Proper heat process and shortening of diffusion distance are effective to distribute inserted Ti-uniformity in Chevrel phase and to decrease secondary phase. According to these analyses, the suitable condition to obtain optimum Chevrel phases, the insert mechanism of cations into the cavities, and the effect of the insertion range of Ti on thermoelectric properties are discussed