Enhanced luminescence and structure evolution of double perovskite (K, Na)LaMgWO₆:Eu³⁺ phosphor for white LEDs

Double perovskite KLaMgWO₆:Eu³⁺ phosphors were successfully synthesized by an improved sol–gel method using citric acid and polyethylene glycol as complexing agents. The structure evolution and photoluminescence were systematically invested by X-ray diffraction, Rietveld refinement and fluorescence spectra. The structure of Eu³⁺ doped samples was double-perovskite with space group C2/m. Enhanced luminescence properties were gotten by adding 5.0 wt% PEG. Na⁺ with smaller radius was selected to substitute K⁺ in this novel host. With increasing the concentration of Na⁺, the tolerance factors decreased and the structure of BO₆ tilted gradually and lowered structure symmetry. Then the emission intensity ratio of ⁵D₀–⁷F₂/⁵D₀–⁷F₁ transition increased and the red emission played the dominate role. Also the emission intensity was enhanced by increasing the concentration of Na⁺. The phosphors showed better color purity with better CIE chromaticity coordinates. Therefore the synthesized phosphors is a potential light conversion red material for light emitting diode.