Photoluminescence of annealed LLGG:Cr3+ crystals under high pressure

High pressure photoluminescence has been used for analysis of lattice disorder in La2.7Lu2.29Cr0.01Ga3O12 and La2.32Lu2.59Cr0.02Ga3.07O12 crystals. Photoluminescence of samples before annealing and those annealed for 5 h in oxygen and hydrogen atmosphere at 923 K has been measured. The pressure dependence of Cr3+ luminescence has been used to obtain the crystal field distribution (lattice disorder) and its dependence on the thermal treatment. The distribution energy of the 4T2 state has been considered as a measure of disorder. Annealing in oxygen has been found to reduce the energies of 4T2 states for all sites, and annealing in hydrogen - to increase these energies.