Energy transfer from Tb3+ to Eu2+ in Ga2S3:(Eu2+, Tb3+) crystals

The photoluminescence of Ga2S3 crystals activated with Eu2+ and Tb3+ ions separately and with ions of both types is studied in the temperature range 77-300 K. It is established that, in the range 77-300 K, the observed broadband photoluminescence in (Ga2S3)(0.95):(Eu2O3)(0.05) crystals with a peak at 545 nm is defined by 4f (6)5d-4f (7)((8) S (7/2)) intracenter transitions in Eu2+ ions and the photoluminescence with peaks at 492, 544, 584, 625, and 680 nm in (Ga2S3)(0.99)(Tb2O3)(0.01) crystals is due to the 5d -> (2) F (j) (j = 6-2) intracenter transitions in Tb3+ ions. It is shown that the photoluminescence bands of Tb3+ ions in the (Ga2S3)(0.94)(Eu2O3)(0.05)(Tb2O3)(0.01) crystals disappears because of excitation energy transfer from Tb3+ ions to Eu2+ ions; i.e., the Tb3+ ion is a sensitizer of the photoluminescence of the Eu2+ ion.