Phase transitions in yttrium oxide at high pressure studied by Raman spectroscopy

Raman spectra of Y2O3 single crystal were recorded at room temperature in a diamond anvil cell up to a pressure of 22 GPa. Two phase transitions were detected at pressures of 12 and 19 GPa. The different phases were identifie d with the three structures exhibited by rare-earth (RE) sesquioxides: cubi c (C-type), monoclinic (B-type), and rhombohedral (A-type) phases. The firs t transition corresponds to the C-->B transformation and the second transit ion to the B-->A transformation. The reversibility of the two phase transit ions as well as the evolution of the Y-O bonds under high pressure is discu ssed. (C) 2000 Elsevier Science Ltd.