Thermoelectric properties of a clathrate compound Ba8Cu16P30

Abstract

We report the electrical resistivity (ρ), thermoelectric power (S), thermal conductivity (κ), and specific heat (C) for the clathrate compound Ba 8 Cu 16 P 30 , in which polyhedral cages are composed of Cu and P atoms. Being in contrast to the n-type conduction in most of clathrate compounds, a p-type metallic conduction in this compound is indicated by the positive S, which monotonically increases up to 65 μV/K at 460 K. The analysis of C(T) gives indirect evidence for low-frequency local vibrations of Ba atoms with two Einstein temperatures 120 and 90 K, respectively. These local vibrations lead to a low lattice thermal conductivity of 2.9 W/K m at 300 K. The combination of the metallic resistivity, large thermoelectric power, and low thermal conductivity, makes this compound be a prospective thermoelectric material.