Structural and luminescent properties of Eu2+ and Nd3+-doped mixed alkaline earth aluminates prepared by the sol-gel method

Abstract

Dedicated to the memory of Prof. Dr. Jurij V. Bren~i~. AbstractAlkaline earth aluminates with the overall nominal compositions Mg 0.5 Sr 0.5 Al 2 O 4 (MSA), Ca 0.5 Mg 0.5 Al 2 O 4 (CMA) and Ca 0.5 Sr 0.5 Al 2 O 4 (CSA) doped with 0.5 mol% of Eu 2+ and 0.25 mol% of Nd 3+ ions were obtained by a modified aqueous sol-gel method and annealed in a reducing atmosphere at 900, 1000, 1100 and 1300 °C. The sample structures were investigated by XRD. Solid solubility was only confirmed for the CSA samples. UV-excited luminescence was observed in the blue region (λ = 440 nm) in the samples of CMA containing the monoclinic CaAl 2 O 4 phase and in the green region (λ = 512 nm) in the samples of MSA containing hexagonal or monoclinic phases of SrAl 2 O 4 . The CSA samples, besides the blue region, exhibited an extended shoulder in the green region, which proved the existence of some pure strontium phases. Co-doped Nd 3+ ions did not affect the wavelength of the emitted light, but the persistent luminescence at room temperature was greatly extended with respect to the aluminates doped with Eu 2+ ions only.