Luminescence Properties of CaAl₂O₄:Eu³⁺, Gd³⁺ Phosphors Synthesized by Combustion Synthesis Method

Abstract

CaAl2O4:Eu 3+ (1 mol.%) co-doped with varying concentration of Gd 3+ (1, 2, 5, and 10 mol.%) were prepared by combustion synthesis method at 600 C and further annealed at 1000 C. All the compositions were investigated for their structural and photoluminescence properties. It was observed that both states of europium i.e. Eu 3+ and Eu 2+ were present and ratio of these states changes on heating at 1000 C. The materials synthesized at 600 C showed high intense peak around 440 nm due to presence of Eu 2+ and less intense peaks in the red region which were due to presence of Eu 3+ . On annealing the compounds at 1000 C, intensity of peak around 440 nm decreases and intensity of peaks in the red region increases significantly. The 5 D0 7 F3 transition due to Eu 3+ at 657 nm appears as the highest intensity peak. All co-doped samples annealed at 1000 C showed the higher intensity than the mono doped sample which is due to energy transfer from the Gd 3+ to Eu 3+ . The second rare-earth ion (Gd 3+ ) acts as sensitizer and enhances the photoluminescence intensity. The X-ray diffraction spectra reveal the monoclinic phase of CaAl2O4 in all the samples which showed that Eu 3+ and Gd 3+ do not change the crystalline structure of calcium aluminate.