Full Length ArticleEnhanced luminescence intensity of CaSi2O2N2: Eu2+ phosphor by using flux in the preparation process and incorporating Gd3+ ions

In this study, CaCl2, NH4Cl, and CaF2 were selected as the flux respectively to assist the preparation of the yellow emitting phosphor of CaSi2O2N2:Eu2+ by the solid-state reaction method. The influence of flux nature on the crystalline structure, morphology and photoluminescent behavior of the CaSi2O2N2:Eu2+ was extensively investigated. Results proved that adding flux can significantly enhance the crystallinity and the emission intensity of the resultant powders. Pure and well crystallized CaSi2O2N2:Eu2+ was formed by using CaCl2 flux at a relatively low temperature (1250 °C) and gave much enhanced yellow emission intensity than that in other samples (around 1400 °C). Further increase of the emission intensity was achieved by the Gd3+ doping. The experimental results showed that the doping of a certain amount of Gd3+ can expand the lattice and improve the absorption and emission intensity of CaSi2O2N2:Eu2+. When the Gd3+ content (x) increases up to 0.04 the luminescence intensity reaches maximum which is about 2 times as that of the phosphor without Gd3+ doping. A white light LED lamp using the optimal phosphor (Ca0.89Eu0.05Gd0.04Si2O2N2) had the color temperature of 5100 K with luminous efficiency of 41 lm W-1 and color rendering index of Ra=76, indicating that Ca0.89Gd0.04Si2O2N2:0.05Eu2+ is a good candidate yellow emitting down-conversion phosphor for white LEDs application.