Preparation and Thermoelectric Properties of Chevrel-Phase CuxMo6S8 (2.0 ≤ x ≤ 4.0)

Chevrel-phase sulfides CuxMo6S8, where 2.0 <= r <= 4.0, were prepared by reacting appropriate amounts of Cu, Mo, and MoS2 powders at 1273-1523 K for 8 h in vacuum. The samples were then densified by pressure-assisted sintering at 1223-1473 K for I h at a pressure of 30 MPa in vacuum. The density of all the sintered samples was greater than 95% of the theoretical density. X-ray analysis showed that all the sintered samples consisted entirely of the hexagonal Chevrel phase. The value of the lattice parameters a and c increased with the Cu content. Measurement of the Seebeck coefficient, electrical resistivity, and thermal conductivity was carried out on single-phase sintered CuxMo6S8 samples in the temperature range of 300-950 K. All the sintered samples had a positive Seebeck coefficient. Further, the thermoelectric properties improved when the Cu content was increased. With an increase in the Cu content, the Seebeck coefficient and electrical resistivity increased, while the thermal conductivity decreased. The highest dimensionless thermoelectric figure of merit ZT (0.4) was observed in Cu4.0Mo6S8 at 950 K. [doi:10.2320/matertrans.MAW200918]