Effect of temperature on the luminescence processes of SrAl2O4:Eu2

The UV excited and persistent luminescence properties as well as thermoluminescence (TL) of Eu2+ doped strontium aluminates, SrAl2O4:Eu2+ were studied at different temperatures. Two luminescence bands peaking at 445 and 520nm were observed at 20K but only the latter at 295K. Both Sr-sites in the lattice are thus occupied by Eu2+ but at room temperature efficient energy transfer occurs between the two sites. The UV excited and persistent luminescence spectra were similar at 295K but the excitation spectra were different. Thus the luminescent centre is the same in both phenomena but excitation processes are different. Two TL peaks were observed between 50 and 250°C in the glow curve. Multiple traps were, however, observed by preheating and initial rise methods. With longer delay times only the high temperature TL peak was observed. The persistent luminescence is mainly due to slow fading of the low temperature TL peak but the step-wise feeding process from high temperature traps is also probable.