High pressure and temperature X-ray diffraction studies on CdTe

The P-T phase diagram of CdTe has been determined by energy dispersive X-ra y diffraction using synchrotron radiation at pressures up to 5 GPa and temp eratures up to 1173 K. We have confirmed the existence of an intermediate c innabar phase between the zinc-blende and the rock-salt phases, as reported previously in a room temperature study. This intermediate phase appears on ly in a very narrow pressure range and can be isolated only in the pressure decrease. We show that there is a quickly reduction of the pressure range in which the cinnabar phase is observed as the temperature is increased. As a matter of fact, at 773 K and above, the transition occurs directly betwe en the zinc-blende and rock-salt phases, showing the existence of a triple point (2.6 +/- 0.1 GPa, 735 +/- 20 K) involving the three solid phases. Abo ve that triple point the solid phase transition boundary compares very well with the results obtained by resistance measurements as well as with the s olid-solid-liquid triple-point coordinates determined by differential therm al analysis.