Sol-gel processed Eu2+-doped alkaline earth aluminates

Sol-gel preparation, structure and luminescence of Eu2+ doped calcium aluminate (CaAl2O4:Eu2+) was studied. The reaction threshold temperature was about 500degreesC, when using the sol-gel method. Unusual metastable hexagonal CaAl2O4:Eu2+ (lattice parameters a=8.74 and c=8.08 Angstrom), was obtained with the sol-gel method. The broad band UV excited luminescence of the hexagonal CaAl2O4:Eu2+ was observed at the blue region (lambda(max) = 448 nm) due to transitions from the 4f(6)5d(1) to the 47 configuration of the Eu2+-ion. The afterglow band position, shape and width were the same as those in the UV excited spectrum indicating the same luminescent Eu2+ centre. The thermoluminescence curve of the hexagonal modification contained several high temperature peaks, which explain the slow decay of the afterglow. (C) 2002 Elsevier Science B.V. All rights reserved.