Study On Synthesis And Luminescence Performances Of Rare Earth Vanadate Red Phosphors Ca₉R（VO₄）₇:Eu³⁺

Rare earth vanadate widely used in the luminescent materials because of its high chemical stability, good thermal stability, excellent luminescence properties and other characteristics. In this thesis, the rare earth vanadate phosphors of Ca9R(VO4)7: Eu3+ have been synthesized by sol-gel method and high temperature solid-state reaction method. The phase structure and luminescent properties of phosphors have been investigated in detail. The main contents include three aspects,the preparation of phosphors by sol-gel method, luminescence properties, and co-doping with Sm3+ ion as a sensitizer.(1) The sol-gel synthesis process of Ca9Gd(VO4)7: Eu3+ phosphors have been explored intensively. The optimal results show that: the sintering temperature is 900℃; the synthetic time is 8 hours; the p H in the range of 6-7; the molar ration of citric acid and metal ions is 1.5; an appropriate amount of PEG can improve not only the dispersion of the sample, but also the luminous intensity.(2) Series of phosphors Ca9R(VO4)7: Eu3+(R = Y, La, Gd) have been synthesized by sol-gel method and their luminescent properties have been studied. The excitation spectra show a broad absorption peak of VO43- groups within the range of 200-370 nm and several Eu3+ ions f-f transition sharp excitation peaks. The phosphors can be effectively excited with a light in the range of near ultraviolet to blue and emit red light. The efficient energy transfer occurs from VO43- groups to Eu3+. The excitation bands match with near ultraviolet and blue LED chips. In addition, the electric dipole transition 5D0â†'7F2 at 620 nm of Eu3+ in the emission spectrum is dominant, which indicates that Eu3+ ions occupy non-inversion symmetry sites in the crystal lattice. Moreover, no concentration quenching is found in the phosphor.(3) Ca9Gd(VO4)7:Sm3+ and Ca9Gd(VO4)7:Eu3+, Sm3+ phosphors have been synthesized by conventional solid-state method, and their luminescent properties have been studied. The excitation and emission characteristic peaks of Sm3+ can be observed in Ca9Gd(VO4)7:Sm3+ fluorescence spectra. While in the fluorescence spectra of Eu3+-Sm3+ co-doped samples, we hardly observe Sm3+ characteristic peaks. What’s more, the emission intensity of co-doped phosphor has greatly been improved, indicating the existence of energy transfer between Sm3+-Eu3+ with Sm3+ as a sensitizer.