Synthesis and photoluminescence properties of red emitting phosphor La_2–xEu_xLi_0.5Al_0.5O₄ [x = 0.2–2] with K₂NiF₄ structure

Abstract

Europium (Eu) -substituted La Li Al O red emitting phosphors were prepared by a conventional high-temperature solid-state reaction method. Powder X-ray diffraction, diffuse reflectance spectra and spectrofluorometry were used as vital characterizing tools for the phosphors. The Eu concentration dependence luminescence properties and Judd-Ofelt intensity parameters were investigated and calculated, respectively. All compositions showed an orange red emission (due to the magnetic and electric dipole transitions of the Eu ion) with the appropriate Commission Internationale de l'Eclairage (CIE) colour gamut under near ultraviolet or blue ray light excitation. The calculated critical distance showed that the energy transfer occured between Eu to Eu via an exchange mechanism. The Eu La Li Al O composition showed the highest red emission intensity with CIE colour saturation compared with that of the commercial Eu-activated yttrium oxysulfide red phosphor.