Enhanced blue emission and EPR study of LaMgAl11O19:Eu phosphors

Europium doped LaMgAl11O19 phosphor was prepared by the combustion method. The as-prepared and post-treated (1350 oC 10 h 5% H2+95% N2) phosphors were investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), photoluminescence (PL) and electron paramagnetic resonance (EPR) techniques. XRD patterns show that LaMgAl11O19:Eu phosphors have hexagonal structure. FT-IR spectrum exhibits absorption bands corresponding to the stretching vibration of AlO4 and AlO6. Morphological studies reveal that this phosphor has faceted plates of varying sizes and shapes. The as-prepared LaMgAl11O19:Eu phosphor consists of both Eu3+ and Eu2+ ions. The phosphor exhibits a bright blue emission at 450 nm (4f65d→4f7 transition of Eu2+). On post-treating the phosphor we are able to enhance the blue emission efficiency by 330%. The process was detected from the evolution of excitation, emission and EPR spectra and the results are discussed.