d-f luminescence of Ce3+ and Eu2+ ions in BaAl2O4, SrAl2O4 and CaAl2O4 phosphors

Ce3+ and Eu2+ doped alkaline earth aluminates MAl2O4 (M = Ca, Sr, Ba) were prepared by single-step combustion synthesis at low temperature (600 A degrees C). X-ray diffraction (XRD) analysis confirmed the formation of BaAl2O4, CaAl2O4, and SrAl2O4. Photoluminescence spectra and optimal luminescent properties of Ce3+ and Eu2+ doped MAl2O4 phosphors were studied. Relation between Eu2+ and Ce3+ f-d transitions was explained. Spectroscopic properties known for Ce3+ were used to predict those of Eu2+ by using Dorenbos' method. The values thus calculated were in excellent agreement with the experimental results. The preferential substitution of Ce3+ and Eu2+ at different Ba2+, Sr2+, Ca2+ crystallographic sites was discussed. The dependence of emission wavelengths of Ce3+ and Eu2+ on local symmetry of different crystallographic sites was also studied by using Van Uitert's empirical relation. Experimental results matched excellently with the predictions of Dorenbos' and Van Uitert's models.