THERMOELECTRIC PROPERTIES OF BORON PHOSPHIDE

This paper describes the thermoelectric properties of boron phosphide wafers prepared using chemical vapor deposition and the thermal constants of a sintered boron phosphide specimen prepared using the r.f. hot pressing technique. The electric conductivity of the n-type boron phosphide wafers increases with temperature, becomes constant and then begins to decrease with temperature. In p-type wafers the conductivity increases with temperature and with a further increase in temperature the intrinsic conduction region is reached. The absolute thermoelectric power of n-type materials has an almost constant value of 500 μV K-1, but it begins to decrease at a temperature of 650 K owing to the creation of acceptors. The thermoelectric power of p-type materials decreases with increasing temperature, indicating that acceptors and donors contribute to the conduction. Thermal constants were obtained by the laser flash method and were measured using sintered disks as standards. Thermal diffusivity, heat capacity and the corresponding calculated thermal conductivity have an accuracy within ±5 percent up to 700°C.