| In this thesis, by choosing alkali-earth and alkali metal molybdate as hosts, red-emitting alkali-earth metal molybdate phosphors and novel single-phased white light phosphors with uniform morphology and particle size were successfully synthesized via a facile surfactant-assisted hydrothermal method. The main research achievements are listed as follows:1. Ellipsoid-shaped CaLa1.65(MoO4)4:0.35Eu3+ red emission phosphors with the particle size of 4 μm were synthesized via a facile glutamic acid-assisted hydrothermal method for the first time. The amounts of glutamic acid (GA), the mole ratios of La3+/MoO42- and the reacting time had a significant effect on the morphology and size of the final products. At the same time, the plausible growth mechanism of the uniform CaLa2(MoO4)4 microellipsoid was proposed to be "nucleation,self-aggregation, dissolution and recrystallization". Besides, the luminescence properties of ellipsoidal CaLa2(MoO4)4:Eu3+ with different morphologies and varied doping concentrations were also investigated. It was found that the optimum concentration of EuCU was 0.35 mmol and the concentration quenching was caused by the electric quadrupole-quadrupole (q-q) interaction. Furthermore, the CIE coordinate of CaLa, 65(Mo04)4:0.35Eu3+ excited at 394 nm was examined to be (0.661, 0.338), which iscloser to the standard red point (0.67, 0.33). Finally, as-obtained CaLa1.65(MoO4)4:0.35Eu3+presented the average luminescence lifetime of 420.7 μs and the higher quantum efficiency of 66.92%, respectively.2. Bipyramid-like CaGd1.85(MoO4)4:0.15Sm3+ with the particle size of 5.5 μm red emission phosphors were prepared by a facile EDTA-assisted hydrothermal method for the first time.We have studied mainly the influence of the amounts of EDTA and the hydrothermal time on the morphology and size of the final products and also proposed the the growth mechanism of the uniform CaGd1.85(MoO4)4:0.15Sm3+ bipyramid-shaped structure,which is "nucleation,self-aggregation,dissolution and recrystallization". Furthermore, the luminescence properties of Bipyramid-like CaGd1.85(MoO4)4:0.15Sm3+ with different morphologies and varied doping concentrations were also investigated. And the optimum concentration of Sm3+ was 0.15 mmol. Among these products, CaGd1.85(MoO4)4:0.15Sm3+presented the strongest emission. The average luminescence lifetime and quantum efficiency of CaGd1.85(MoO4)4:0.15Sm3+are 600.58 μs and 43.5%, respectively.3. The spherical Sm3+/Dy3+ co-doped single-phased NaLa0.87(MoO4)2: 1%Sm3+,12%Dy3+white light phosphors were hydrothermally synthesized by the EDTA mediated method. We have investigated the concentration of Sm3+/Dy3+ single or co-doped in NaLa (MoO4)2 hosts on their luminescent protperties. Under the excitation of 297 nm, the quenching concentration of Sm3+ in NaLa(MoO4)2 host was determined to be 13% and the concentration quenching mechanism was discussed to be the electric quadrupole-quadrupole interaction. By varying co-doping concentrations of Sm3+/Dy3+ ions,the emission color of NaLa(MoO4)2:Sm3+,Dy3+can be tuned from reddish-orange,pink,white to bluish-green. The CIE chromaticity coordinate of NaLa0.87(MoO4)2:1%Sm3+,12%Dy3+ was calculated to be (0.356, 0.320),which is closer to be standard white point (0.33, 0.33). Finally, we have investigated the correlated color temperature (CCT) and quantum efficiency of NaLa0.87(MoO4)2:1%Sm3+,12%Dy3+which are 4353 K and 20%, respectively. Furthermore, based on the temperature dependent analysis, it presented good thermal stability. |
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