High pressure transition in cadmium telluride

Abstract

The zinc blende--rock salt phase boundary of a single crystal of cadmium telluride was investigated experimentally over the P, T range up to about 35kb and 800℃ by observing the electrical resistance behavior in a cubic compact anvil device. In single crystal samples the room temperature transition pressure is found to be 33.3±1.8kb, At the transition the electrical resistance decreases by several orders of magnitude. The magnitude of the resistance change at the transition decreases with increasing temperature. In the pressure-temperature phase diagram the zinc blende--rock salt phase boundary has a slope of -0.015kb/deg. The phase boundary, determined in the range from room temperature to 800℃, is a straight line that may be extrapolated nearly to the triple point between the liquid and two solid phases of CdTe reported by Jayaraman et al. The heat of transition at room temperature calculated from the Clapeyron equation is 6.6×10^2cal/mole. The change in entropy is found to be 2.3 e. u. From the measurements of electrical resistance as a function of temperature, it is found that the energy gap of CdTe of the zinc blende phase is about 1.3eV and it increases with pressure.