Luminescence properties of CaAl2O4:Eu3+, Gd3+ phosphors synthesized by combustion synthesis method

Abstract

CaAl2O4:Eu3+ (1 mol.%) co-doped with varying concentration of Gd3+ (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. Eu3+ and Eu2+ 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 Eu2+ and less intense peaks in the red region which were due to presence of Eu3+. 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 5D0 !7 F3 transition due to Eu3+ 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 Gd3+ to Eu3+. The second rare-earth ion (Gd3+) 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 Eu3+ and Gd3+ do not change the crystalline structure of calcium aluminate.