Characterization and Luminescence Properties of Blue Emitting Phosphor (Mg,Sr)Al2O4:Eu2+ for White LEDs

Mg1-x-ySryAl2O4:Eu-x(2+) blue phosphor particles for white light-emitting diodes (LEDs) were prepared by a solid-state reaction method, and their luminescent properties were investigated with the change in the concentration of the activator and the composition of the host matrix. The phosphor particles were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, and fluorescence spectrophotometer. The luminescence of Eu2+-activated MgAl2O4 has shown a strong blue emission dominant peak around 460 nm, and the highest intensity was observed when the content of Eu2+ was 2 mol %. The substitution of 1-10% Sr2+ ions instead of the Mg2+ greatly enhanced the 460 nm blue emissions, especially for samples excited by UV in the range of 350-400 nm. The optimized phosphor Mg0.92Sr0.06Al2O4:Eu-0.02(2+) has shown 10 times emission intensity compared with that of the Mg0.98Al2O4:Eu-0.02(2+) phosphor when they were excited by a 365 nm UV light. The luminescent properties of Mg1-x-ySryAl2O4:Eu-x(2+) were investigated by changing the ratio of Sr2+ to Mg2+. For Sr2+-doped MgAl2O4:Eu2+, the photoluminescence increased by about 6%. The mechanism for the improvement was discussed. No obvious degradation problem of the synthesized Sr2+-doped samples due to the moisture in the laboratory atmosphere could be found.