High pressure investigation of the LLGG:Cr3+ crystals after heat treatment

La2.32Lu2.59Cr0.02Ga3.07O12 crystal has been annealed in hydrogen atmosphere at 823 K during 4 hours. We have measured high pressure photoluminescence spectra of as grown and annealed crystals under pressures from ambient to 200 kbar at 20 K. For pressure above 70 kbar a broad band emission related to the 4T2→4A2 transition in the Cr3+ has been replaced the sharp R lines emission related to the 2E→4A2 transition. Analysis of the R1 line structure allowed distinguishing five nonequivalent Cr3+ sites. It has been also found that annealing in H2 atmosphere caused increase of the crystal field strength 10Dq and/or decrease of electron-lattice coupling in all Cr3+ sites with respect to as grown material. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)