Study On Synthesis And Photoluminescence Properties Of Ca₉La?VO₄?₇:Eu³⁺ Luminescent Material

There are two outstanding features in the vanadate doped with Rare-earth ions because of the T_d symmetry of the[VO₄]^3-in the vanadate host luminescent materials:?1?the self-activated process of O^2-?V⁵⁺CT would be enhanced by a distorted Td symmetry after doping with rare-earth ions;?2?in the self-activated process of O^2-?V⁵⁺CT,the[VO₄]^3-will transform energy efficiency to the activator.Rare-earth vanadate host luminescent materials have become an important optical materials and widely used as luminescent material due to their high luminous efficiency,rich colors,excellent chemical and thermal stability.Although YVO₄:Eu³⁺red-emitting phosphors has achieved commoditization,the high cost limits its application.In this paper,the Ca₉La?VO₄?₇:Eu³⁺was choosen as research object due to its abundant reserves and low cost.The samples were prepared by the citric acid-fueled combustion method and characterized by TG,XRD,SEM and fluorescence spectra.The condition of synthesis and luminescent properties were optimized.The Ca₉La?VO₄?₇:Eu³⁺materials with high luminescence property and excellent thermal stability were synthesized at 900?for 1h in conjunction with the citric acid dosage 2n?NH₄VO₃?+1.6 n(Ca²⁺+La³⁺).The emission spectra of the samples shown a dominant wavelength of 618 nm due to ⁵D₀?⁷F₂ of Eu³⁺under the excitation by blue light of 464 nm.The thermal activation energy of samples was 0.28 eV that exhibit good thermal stability.The luminescence properties were significantly influenced by doping with Eu³⁺,the luminous intensity would increase with the concentration of Eu³⁺increase.To modify the Ca₉La?VO₄?₇:Eu³⁺phosphors by doping positive ions Mg²⁺,Sr²⁺,Ba²⁺,Zn²⁺which substitute for Ca²⁺and negative ions[PO₄]^3-which substitute for[VO₄]^3-.All of them did not change the crystal structure of the samples?trigonal system,the space group is R₃?in the concentration range of this paper.But they can significantly enhance the luminescent properties.The luminescent intensity would be the best when the doping contents of Mg²⁺,Sr²⁺,Ba²⁺,Zn²⁺were 0.2 mol,0.1 mol,0.1mol,0.12 mol and 0.15 mol,which are 1.7,1.8,1.3,1.9,and 1.5 higher than Ca₉La?VO₄?₇:Eu³⁺phosphors respectively.The(Ca_0.88Zn_0.12)₉La?VO₄?₇:0.1Eu³⁺red-emitting phosphors synthesized in the optimized conditions was encapsulated as white LED by combining with YAG:Ce³⁺yellow-emitting phosphors coating on a single ultraviolet chip and packaging by epoxy resin.The controlling temperature and CRI were investigated.The results shown the samples have excellent controlling color temperature and color rendering index and is a potential red-emitting phosphor applied with blue LED.