Study On The Preparation And Luminescenct Properties Of Vanadate Based Phosphors For White LED

The vanadate matrix have stable chemical and physical properties,and most vanadate matrix have the advantages of emitting blue green light and transmitting energy effectively to activator ions under ultraviolet light excitation,which make it become a hot spot in the field of fluorescent material research.In this paper,a series of WLED phosphors based on vanadate has been synthesized by high temperature solid-state reaction.The main research contents are as follows:?1?Sr₃La?VO₄?₃:Eu phosphors have been prepared by high temperature solid phase method.The phosphors show strong blue green emission of vanadate ion and red emission of Eu³⁺ion under ultraviolet light excitation.By doping anions(MoO₄^2-,WO₄^2-,PO₄^3-)and cations(Y³⁺,Gd³⁺,Tb³⁺),the intensity ratio of red and blue green light can been regulated and a single matrix white light phosphor can been obtained.XRD test results indicate that doping a small amount of anions(MoO₄^2-,WO₄^2-,PO₄^3-)and cations(Y³⁺,Gd³⁺,Tb³⁺)ions can not change the crystal structure of the matrix.The luminescent test shows that doping a certain amount of MoO₄^2-and WO₄^2-can weaken the blue emission of VO₄^3-obviously,but has little effect on the red emission of Eu³⁺.Doping a proper amount of PO₄^3-can weaken the spontaneous quenching of VO₄^3-,which is beneficial to the energy transfer fromVO₄^3-to Eu³⁺.Considering the emergent of charge imbalance,the charge compensating agent F^-ions is added simultaneously with doping of MoO₄^2-and WO₄^2-ions.Byadding F^-ions to balance charge,the red emission of Eu³⁺enhances with the MoO₄^2-concentration increasing,at the same time,the blue emission of VO₄^3-first increase,then decrease.Adding F^-ions to compensate the charge imbalance caused by WO₄^2-doping shows little effect on the the red emission of Eu³⁺,but can significantly reduce the emission of VO₄^3-.Excitation and emission peaks of VO₄^3-exhibit different degrees of red shift with different concentrations of MoO₄^2-and WO₄^2-doping.Doping Y³⁺,Gd³⁺and a small amount of Tb³⁺can improve the luminescent properties of Eu³⁺and the effect of Y³⁺and Gd³⁺is very significant.Under ultraviolet light excitation,using doped MoO₄^2-,WO₄^2-,PO₄^3-,Y³⁺,Gd³⁺and Tb³⁺to change the emission intensity proportion of VO₄^3-and Eu³⁺can been adjusting by doping MoO₄^2-,WO₄^2-,PO₄^3-,Y³⁺,Gd³⁺and Tb³⁺,and a single phase white light phosphor can been obtained.?2?A series of Tm³⁺,Dy³⁺,Sm³⁺,Tb³⁺and Eu³⁺single doped,Tm³⁺-Eu³⁺,Tm³⁺-Sm³⁺,Tm³⁺-Dy³⁺,Dy³⁺-Eu³⁺and Dy³⁺-Tb³⁺co-doped,and Mg²⁺,Sr²⁺doped in Ca₃La?VO₄?₃ phosphors have been synthesized by high temperature solid method.The rare earth ion single doped Ca₃La?VO₄?₃ samplesemit the characteristic emissions of the rare earth activator ions the emission of Tm³⁺ion is weak and that of other doped rare earth ions strong.Co-doped Tm³⁺-Eu³⁺,Tm³⁺-Sm³⁺,Tm³⁺-Dy³⁺,and Dy³⁺-Tb³⁺can obtain near white light emitting single matrix phosphor.The red and yellow emitting can be obtained by changing the Dy³⁺concentration in the Dy³⁺-Eu³⁺co-doping system.In the Ca₃La?VO₄?₃:Eu³⁺system,doping Mg²⁺or Sr²⁺with different radius to replace the Ca²⁺can improve the luminescence of Eu³⁺,when the Mg²⁺doping amount xis 0.3,the matrix exhibits a strong blue green light emission,a single substrate white light emitting phosphor can be obtained at this doping concentration.?3?A series of Ca_3x/2La_3-x?VO₄?₃:0.01Eu³⁺?x=0³?phosphors have been synthesized by high temperature solid phase method.Monoclinic structure of La VO₄,hexagonal system of Ca₃La?VO₄?₃ and Ca₃?VO₄?₂ can be obtained under the temperature range from 800^oC to 1100^oC and time range from 3h to 6h.Under the synthesized conditions of 1000 ^oC and 5h,the system from LaVO₄ to Ca₃La?VO₄?₃ and to Ca₃?VO₄?₂ can been obtained by changing the ratio of La³⁺and Ca²⁺.In the transforming process from La VO₄ phase to Ca₃La?VO₄?₃ phase,the broadband excitation peak appears red shift in the excitation spectrum,and the Eu³⁺emission is originated from ⁵D₀?⁷F₂ electric dipole transition mainly.In general,the Eu³⁺transition emission increases first and then weakens,the Eu³⁺have strongest emission when x is1.?4?A series of NaMg_4-xCa_x?VO₄?₃:0.01Eu³⁺?x=0²?,NaMg_2.1Ca_1.9-y?VO₄?₃:yEu³⁺?y=0⁰.19?,NaMg_2.1Ca_1.9-y?VO₄?₃:yEu³⁺,xX^-?X=Cl,F?and Na Mg_2.1Ca_1.9-x-y?VO₄?₃:y Eu³⁺,xM⁺?M=Li,Na,K?phosphors have been synthesized by high temperature solid phase method,the phosphors can emit the blue green light of vanadate ions and the red light of europium ions simultaneously.In NaMg_4-xCa_x?VO₄?₃:0.01Eu?x=0²?phosphors,both the emission intensity of matrix and Eu³⁺first increase and then weakene,and the emission peak take place blue shift.In NaMg_2.1Ca_1.9-y?VO₄?₃:yEu³⁺system,when Eu³⁺doping content y is 0.133,the energy transfer efficiency is42.21%,indicating that the energy transfer from VO₄^3-to Eu³⁺is effective,and the energy transfer mechanism is dipole-dipole interaction.With the increase of Eu³⁺concentration,the CIE coordinates move from the blue light area to the white light region.Adding F^-,Cl^-,Li⁺,Na⁺and K⁺ions as the charge compensator can enhance the emission of Eu³⁺,and the charge compensation effect of cation is better than that of the anion,the charge compensation effect is Li⁺>Na⁺>k⁺>F^->Cl^-.All the CIE coordinates of the samples can be moved to the white light region,indicating that the single phase white light emitting phosphor can been obtained.