High pressure Raman study of Y3Al5O12

The effect of high hydrostatic pressure on Y3Al5O12 (YAG) single crystals has been studied up to 15 GPa by Raman spectroscopy at room temperature. The pressure dependence of 23 Raman-active modes, out of 25 predicted by group theory, has been followed. The determined mode Gruneisen parameters (gamma(i)) extend over a relatively narrow range (0.6-2.4) indicating binding forces of the same nature and order of magnitude. However, the modes in the high (650-900 cm(-1)) and middle (500-600 cm(-1)) regions of the Raman spectrum exhibit gamma(i) parameter values ranging between 0.9-1.4 and 0.7-0.8, respectively; reflecting that different type of AlO4 molecular vibrations and consequently different kind of restoring forces being involved in these modes, in accordance with theoretical predictions. The strength of interactions in YAG along with the high compactness of the garnet structure explains, somehow, their high stability upon pressure. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.