AB2X4 compounds and other new thermoelectric materials studied at JPL

Thermoelectric properties of Mo₆Se₈-based Chevrel phase with semiconducting properties

Y. Ohta¹, J. Rousseau², J Tobola^2,3, 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.