Thermoelectric properties of Mo6Se8-based Chevrel phase with semiconducting properties

Y. Ohta1, J. Rousseau2, J Tobola2,3, P. Pecheur2, H. Scherrer2, I. Iwanaga1, A. Kasama4, Y. Matsumura1

1Japan Ultra-high Temperature Materials Research Institute, 573-3 Okiube, Ube, Yamaguchi, 755-0001, JAPAN

2Laboratoire de Physique des Matériaux, UMR7556, ENSMN, Parc de Saurupt, 54042 Nancy, France

3Faculty of Physics and Nuclear Techniques, University of Mining and Metallurgy, 30059 Krakow, Poland

4Kurume National College of Technology, 1-1-1 Komorino, Kurume, Hukuoka, 830-8555, Japan

Mo6Se8-based Chevrel phase compounds inserted cations into those cavities are interesting as a new kind of PGEC (Phonon Glass Electron Crystal) thermoelectric materials. From band structure calculations, the compositions including TiMo6Se8 have been found to be semiconductor or semimetal, and therefore are expected to have good Seebeck coefficient besides low thermal conductivity. In the previous preparation process of Chevrel phases, it had been apparent that insertion of enough cations to the cavities in Mo6Se8 is difficult due to secondary phase and oxide appearance. We present in this work that estimation of the effect on combination of inserted cations experimentally and theoretically in order to improve thermoelectric properties of Chevrel phases. The raw mixtures of elemental powders were ball-milled, and sintered by spark plasma method with various conditions. The constituent phases and the thermoelectric properties of the sintered materials were evaluated. We used the liner muffin-tin orbital - tight binding (LMTO-TB) method for the theoretical band structure calculations. The potential of Chevrel phases for thermoelectric applications will be discussed.