Structural phase transition of CdS microcrystals embedded in GeO2 glassy matrix under high pressure

CdS microcrystals of various sizes' embedded in a germanium dioxide glass m atrix have been studied by Raman scattering and optical absorption under hi gh pressure up to about 9 GPa. Structural phase transition of the CdS micro crystals from wurtzite to rock salt phase was observed at a pressure higher than 6 GPa, which is far above the bulk CdS transition pressure of 2.7 GPa . Under a pressure higher than 6 GPa, the 1-LO Raman intensity of the wurtz ite phase of CdS microcrystals decreases gradually with time. After the pre ssure is released from about 9 GPa to atmospheric pressure, the high pressu re rock salt phase is preserved at room temperature. We found that CdS micr ocrystals of the rock salt phase recovered to the wurtzite phase by tempera ture annealing at atmospheric pressure. Our observations suggest that the G eO2 matrix plays an important role.