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 identified with the three structures exhibited by rare-earth (RE) sesquioxides: cubic (C-type), monoclinic (B-type), and rhombohedral (A-type) phases. The first transition corresponds to the C→B transformation and the second transition to the B→A transformation. The reversibility of the two phase transitions as well as the evolution of the Y–O bonds under high pressure is discussed.