Thermoelectric power in the normal state of Chevrel-phase superconductors of the type Cu_1.8Mo₆S_8-ySe_y, 0⩽y⩽8, and Cu_1.8Mo₆S_8-yTe_y, 0⩽y⩽4

Abstract

The thermoelectric power, S, of Chevrel-phase superconductors of the type Cu1.8Mo6S8-ySey, 0<y<8, and Cu1.8Mo6S8-yTey, 0<y<4, have been measured between 300K and the superconducting transition temperature. The high-temperature values are found to arise mainly from the diffusion of conduction electrons while at low temperatures phonon-drag contributions are also observed. The diffusion thermopower is interpreted in terms of Mott-Wilson theory and band-structure data. The phonon specific heat has also been measured in the case of Cu1.8Mo6S8 and Cu1.8Mo6S1Se7 and is shown to be proportional to the phonon-drag part of the thermopower.