Preparation and properties of Eu2 +-activated alkaline-earth phosphosilicate phosphors

The Eu2+-activated alkaline-earth phosphosilicates M7−a(PO4)x(SiO4)(14−4x)/3Eua (M=Ba, Sr, Ca) were prepared by solid-state reaction and special attention was paid to the barium phosphosilicate that has higher luminous efficacy than the Sr and Ca analogs. Effects of P/Si ratio, Eu concentration and substitution of Sr or Ca for Ba on phase composition, photoluminescence excitation and emission properties of the phosphor were investigated by using X-ray diffraction, diffuse reflectance spectroscopy, excitation and emission spectroscopy. It was found that M7−a(PO4)x(SiO4)(14−4x)/3Eua phosphors can be excited by near UV and blue radiation (350–420 nm), making them attractive as potential phosphors for white LED applications. A green emission peaking at 507 nm for Ba6.92(SiO4)2(PO4)2Eu2+0.08, and a yellow emission peaking at 549 nm for Sr6.9(SiO4)3.125(PO4)0.5Eu2+0.1 were observed. The emission peak can be adjusted between 502 and 550 nm depending on the compositions. The emission peak yellow shifted with substitution of Sr for Ba accompanied by decrease in intensity. The alkaline earth phosphosilicates were moisture-proof in atmosphere.