Laser excited long lasting luminescence in CaAl2O4: Eu3+/Eu2++ Nd3+ phosphor

Abstract

The europium and neodymium oxides doped nano-structured calcium aluminate phosphor samples have prepared through combustion technique and their luminescence properties are studied using laser excitations. Samples prepared in open atmosphere showed the presence of both Eu3+ and Eu2+ states and their ratio changes with calcination temperature. Single Eu 3+/Eu2+ ions doped sample has found to give broad emission at 450 nm without the persistence glow while the Eu3+ + Nd 3+ ions codoped sample has shown persistence glow at 450 nm (Eu 2+) on 355 nm laser excitation. Wavelength selective excitations show that 266 nm excitation gives the intense emissions from both Eu3+ and Eu2+ states with no afterglow but 355 nm excitation gives negligible emission from Eu3+ ions and a strong afterglow at 450 nm wavelength. The mechanism of wavelength dependent phosphorescence has been discussed. Studies on Stark splittings and their relative intensities in emission spectra of Eu3+ ions have shown that Eu3+ ion can be used as excellent probe of crystal structure. © 2012 Elsevier B.V. All rights reserved.