Low temperature thermoluminescence properties of Eu2+ and R3+ doped CaAl2O4

The thermoluminescence (TL) of calcium aluminate persistent luminescence materials doped with Eu2+ and co-doped with R3+ ions were studied between 20 and 325 K. The basic material, CaAl2O4:Eu2+, showed three TL bands between 150 and 300 K in the glow curve. Changing the R3+ co-dopant to the adjacent element in the rare earth series affects significantly the thermoluminescence intensity and even the position of the glow curve maximum. The physical effect seemed to be removing the traps since the La3+, Y3+, and Lu3+ ions suppressed the thermoluminescence. The Pr3+, Ho3+, and Dy3+ co-doping enhanced mainly the low temperature traps and these materials have an intense but relatively short persistent luminescence at room temperature. The Nd3+ and Tm3+ ions enhanced the TL bands close to room temperature and are thus the most suitable co-dopants to induce intense and long persistent luminescence. The quenching of the thermoluminescence by Sm3+ was concluded to be due to the presence of Sm2+ that removes totally the traps. (C) 2004 Elsevier B.V. All rights reserved.