Luminescence Properties Of Rare-earth Ions Doped Molybdate And Tungstate Luminescent Material

Luminescent materials are widely used in laser, lighting, display and testing, and is expanding toward the emerging field, so the research for rare-earth luminescent materials is particular significance. Due to special structure, high concentration doped with rare earth ions, and great stable performance for molybdate and tungstate luminescence material, the study of luminescent materials used molybdenum tungstate host is attracting more and more interest.Based on the review of the research on molybdate tungstate luminescence materials at home and abroad, the spectroscopic properties and preparation process of some rare-earth ions doped molybdate tungstate luminescence materials were studied. These activated ions include:Sm3+,Dy3+,Eu3+,Yb3+, Tm3+. The hosts are:tetra-molybdate NasY(MoO4)4; tetra-molybdate tungstate Na5Eu(WO4)0.5(MoO4)3.5, Na5Bi(WO4)2(MoO4)2; double-molybdate KLa(MoO4)2; double molybdate tungstate NaGd(WO4)0.5(MoO4)1.5.Some powder samples using Na5Y0.95(MoO4)4 as host were reported. That phosphors single-doped rare earth ions Dy3+,Dy3+,Sm3+ have strong absorption peak at ultraviolet and blue, which just match with the emission spectrum of ultraviolet and blue LED chips. And the two strongest emission peak of Sm3+:Na5Y0.95(MoO4)4 locate at 603 and 644nm respectively.The two strongest emission peak of Dy3+:Na5Y0.95(MoO4)4 locate at～573nm (yellow) and～484nm (blue), and the total color is close to white. The strongest emission peak of Sm3+:Na5Y0.95(MoO4)4 locate at～616nm (red). So they are a very promising fluorescent material for LED.Comparing to single-doped Eu3+, Sm3+, Eu3+ co-doped Na5Y(MoO4)4powder sample not only widened the absorption spectrum, but also enhanced the absorption intensity. Sm3+ ion can absorpt and efficiently transfer energy to the Eu3+, which enhanced luminous intensity of the phosphor. In the same way, Dy3+, Eu3+ co-doped Na5Y(MoO4)4 powder sample is stronger in absorbtion and luminous intensity than Eu3+ single-doped powder sample. There are threeNa5Eu(WO4)0.5 (MoO4)3.5 phosphor samples synthesized at different temperatures(600,700,800℃). Phase of the phosphor sample burned at 600℃. is purest than the other twp samples. As far as luminous performance, the higher temperature, the stronger the absorption intensity and emission peak intensity of the samples.As a sensitizer in the Sm3+,Eu3+ doped LiGd(W04)0..5(MoO4)1..5 phosphor samples, Sm3+ion can effectively absorb and transfer energy to Eu3+ion. The CIE color coordinates of the Sm3+,Eu3+ co-doped phosphor is as well as Eu3+ single-doped phosphor.Polycrystalline material Yb3+:Na5Bi(WO4)2(MoO4)2 has a similar structure with the two quadruple molybdate and tungstate(Na5Y(MoO4)4,Na5Y(WO4)4), and they all belong to the tetragonal system, with space group I41/a. Its melting point is about 930℃and the absorption band, emission band, center emission wavelength, fluorescence lifetime are about 83nm,50nm,1006nm,589.03μs respectively.The Tm3+,Yb3+:KLa(MoO4)2crystal was successfully grown by Czochralski method, but some parameters such as pulling speed,the cooling rate, seed rotation rate were not set properly enough, which cause crystal cracking.