Site dependent thermo luminescence of long persistent phosphorescence of BaAl2O4:Ce3+

A very long persistent phosphor BaAl2O4 : Ce3+ was prepared and studied. The Ce3+ 5d-4f emissions from two Ba2+ sites in the BaAl2O4 were observed at 450 and 402 nm. The lowest 4f-5d excitation peaks were recorded at 357 and 335 nm, respectively. The persistence times of the long afterglow emissions from Ce3+ at the two sites were found to be longer than 10 h. Site-selective thermoluminescence spectra of the sample were measured. Two sets of thermoluminescence peaks were detected at -43, -26 and 27 degreesC, and -53, -36 and 30 degreesC (heating rate 13.3 degreesC/min) corresponding to the two sites at 450 nm (site-1) and 402 nm (site-2), respectively. Dy3+, Ce3+ co-doped samples were also prepared, which introduce new defect-related traps at 18, 50, and 82 degreesC (heating rate 10 degreesC/min). These defect-related traps due to Dy3+ co-doping also contribute to the Ce3+ afterglow at the two sites. (C) 2002 Elsevier Science B.V. All rights reserved.