Thermal and luminescent properties of Eu2+-doped aluminates prepared by the sol–gel method
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Alkaline earth aluminates with the overall nominal compositions Ca0.5Sr0.5Al2O4, Ca0.5Mg0.5Al2O4 and Mg0.5Sr0.5Al2O4 doped with 1 mol% of Eu2+ ions were prepared by the modified aqueous sol–gel method. The thermal behaviour of the xerogels was studied by the TG/DSC-MS technique under an argon and a reductive atmosphere (Ar/H2–5 %). Appropriate luminescent efficiency of the materials was achieved after annealing at temperatures lower than those in conventional solid state reactions. All three aluminates are mixtures of at least two phases; the monoclinic phase of CaAl2O4, the hexagonal phase of SrAl2O4 and the cubic phase of MgAl2O4 were identified. Solid solubility was recognised in the Ca0.5Sr0.5Al2O4:Eu2+ composition due to the similar ionic radii of Ca2+ and Sr2+. UV excited luminescence was observed in the blue region (λmax = 441 nm) in the aluminates containing the monoclinic phase of CaAl2O4 and in the green region (λmax = 520 nm) in the Mg0.5Sr0.5Al2O4:Eu2+ composition.
KeywordsAlkaline earth aluminates Europium Luminescence Sol–gel Thermal decomposition
Financial support from the Slovenian Research Agency (ARRS), Ljubljana, (P-0134) is gratefully acknowledged. The authors are grateful to Prof. Dr. Anton Meden for helpful discussions about XRD analysis.
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