Effects of Ti4+ Ions on Fluorescence Properties of Sr2CeO4:Sm3+ Phosphors

Ti4+-doped Sr2CeO4:Sm3+ phosphors were synthesized with the solid-state reaction method and the effects of doping Ti4+ on the photoluminescence properties were investigated in detail. A broad excitation band ascribed to the O2- -Ce4+ transition was observed in the range of 200 to 400 nm and with doping Ti4+ nto Ce4+ sites, the intensity of charge transfer band of O2- --> Ce4+ (300-370 nm) was significantly broaden and enhanced. As a result, the emission intensity of Sr2Ce1-xTixO4 has improved about 85% by doping 0.01 mol Ti4+. White emission of Sr2-yCe0.99Ti0.01O4:ySm3+ at y < 0.03 is due the co-existence of Ce4+ --> O2- CT emission and 4G5/2-6HJ Sm3+ transitions whereas only the Sm3+ red emission prevails for 0.03 < y ≤ 0.15. The Sr1.99Ce0.99Ti0.01O4:0.01 Sm3+ phosphor exhibited excellent color purity. Its chromaticity coordinate is measured to be (0.326, 0.322), which is close to the pure white (0.33, 0.33). The results showed that Sr1.99Ce0.99Ti0.01O4: 0.01 Sm3+ phosphors could be considered as a potential single-phase white-emitting phosphor for white light-emitting diodes.