Structural evolution of zinc doped cadmium telluride at high pressure and high temperature

Cd0.9Zn0.1Te (CZT) has gained a lot of traction with its application in the field of radiation detectors. In this study, CZT has been investigated using in situ x-ray diffraction(XRD) at high pressures up to 22 GPa, and both high pressure and high temperature (HP HT) up to 5 GPa and 400 degrees C. CZT adopts zinc blende phase at ambient condition. We have observed the previously unreported cinnabar type phase in CZT at high pressure. Cinnabar type phase nucleated at 1.8 GPa because of the motion of Te atoms in the ab-plane of zinc blende CZT and coexisted with the parent phase. The onset of transition to rocksalt phase took place at 4.7 GPa with successive atomic displacement along a and c direction of the cinnabar type unit cell. The parent phase disappeared at 6.3 GPa, but cinnabar type phase as a distorted form of rocksalt phase coexisted with the rocksalt phase due to the comparable energy for both the structures. The mechanism of transitions to cinnabar type and rocksalt phase is of quasi-reconstructive nature. Further, the rocksalt phase underwent a displacive transition to an orthorhombic (Cmcm) phase at 10.7 GPa which is accompanied by expansion along one axis and compression along the other two axes. In the reverse pressure cycle, the transitions were reversible and sluggish in nature. In the in situ high pressure and high temperature XRD studies, distinct structural hysteresis was observed and the transition to rocksalt phase was irreversible. At ambient pressure, the zinc blende structure remained stable up to 400 degrees C. The thermal expansion coefficient of the zinc blende phase and the high pressure rocksalt phase were estimated to be 23(1) x 10-6/degrees C and 10.2(1) x 10-6/degrees C respectively.