Effect of dopant (Li+, Mg2+ and Bi3+) on the photoluminescence emission intensity of Eu3+ doped CaAl2O4 phosphor: Application to white LEDs

Abstract

In this work, we have investigated the photoluminescence (PL) emission properties of Eu3+ doped CaAl2O4 in the presence of singly, doubly and triply ionized dopant ions i.e., Li+, Mg2+ and Bi3+ ions. The phosphor samples were synthesized by the high-temperature solid-state reaction process at 1473 K. The crystalline phase, crystallinity and surface morphology of Li+, Mg2+ and Bi3+ ions doped 0.01Eu3+:CaAl2O4 phosphor were examined and confirmed by X-Ray diffraction (XRD) and scanning electron microscope (SEM) measurements. The different vibrational groups and their corresponding vibrational frequencies were measured by Fourier transform infrared (FTIR) technique. The 0.01Eu3+:CaAl2O4 phosphor emits intense red emission at 616 nm on excitations with 393 nm (Eu3+ line) and by the charge transfer band (Eu3+-O2-) at 262 nm. The overall PL emission intensity of 0.01Eu3+:CaAl2O4 phosphor on excitation with 393 nm is found to increase almost 2.8 times in the presence of Li+ than other dopants. The emission intensity are increased in case of Li+ and Mg2+ doping due to crystallinity, charge compensation and the asymmetry created around the Eu3+ ions in the phosphors matrix. However, in case of Bi3+ ion, the emission intensity decreases on 393 nm excitation. In the presence of Bi3+ ion the intense red emission is observed due to energy transfer from Bi3+ (3P1→1S0) to Eu3+ ion on λexc = 294 nm. The lifetime study were carried in each case which are in accordance with the PL emission behaviour of Li+, Mg2+ and Bi3+ ions doped 0.01Eu3+:CaAl2O4 phosphor. The CIE color coordinates, correlated color temperature (CCT) and color purity have been calculated, which shows highly pure red color in the warm light region. The 0.01Eu3+:0.10Li+:CaAl2O4 phosphor may be used in displays devices, photonic devices, solid state lighting as red light emitting source.