Preparation And Luminescent Properties Of Two-component Rare Earth Co-doped Single-substrate White Phosphors

White LED is considered to be the most promising white light source due to its unique absolute advantages and energy saving potential in the lighting field.Although LED has been commercialized at present,the white LED obtained by compounding the yellow phosphor with the blue chip has the disadvantages of high color temperature and low color rendering index.However,the white LED obtained by compounding the（near）UV chip with the three-color phosphor has a fatal defect such as low luminous efficiency.Therefore,it is of significant practical value to improve the existing phosphor or develop a new white phosphor.In this dissertation,tungstate and molybdate were chosen as the matrix,and two ion-codoped single-substrate white phosphors were synthesized by co-precipitation method and microwave method.The effects of changing the kind of active agent,the amount of addition,and the ratio of rare earth ionic substances on the luminescent properties of phosphors were studied.The different effects of the same reaction conditions on the tungstate matrix and the molybdate matrix were also investigated to find the optimal synthesis conditions for the two substrates.The specific content of this paper mainly includes:（1）Dy³⁺and Eu³⁺co-doped NaLa（WO₄）₂ and NaLa（MoO₄）₂ series white phosphors were synthesized by the improved co-precipitation method.PVP was added to the samples to increase the luminescence intensity of the two phosphors.The characteristic excitation and emission peaks of Eu³⁺ions at 393 nm and616 nm in NaLa（WO₄）₂ are much stronger than those of Eu³⁺ions in NaLa（MoO₄）₂,indicating that the tungstate matrix is more conducive to the energy transfer to Eu³⁺.Adjusting the ratio between the amounts of Dy³⁺and Eu³⁺substances,NaLa（WO₄）₂ obtains the closest chromaticity to the standard color coordinates when the ratio of the amounts of Dy³⁺and Eu³⁺substances is 1:1.NaLa（MoO₄）₂ is closest to the standard color coordinates when the ratio of Dy³⁺and Eu³⁺substances is 1:2.It is shown that Dy³⁺and Eu³⁺doped NaLa（WO₄）₂ and NaLa（MoO₄）₂ are excellent white phosphors excited by near-ultraviolet light.（2）Dy³⁺,Eu³⁺co-doped SrWO₄ and SrMo O₄ series white phosphors were prepared by microwave method,and glutamic acid was determined as the active agent and the optimal addition amount was 0.375 g.At the same time,it was found that the characteristic excitation and emission peaks of Eu³⁺ions at 393 and616 nm in tungstates in NaLa（W/MoO₄）₂ are much stronger than the characteristic emission peaks of Eu³⁺ions in molybdates.SrW/MoO₄ is also present,demonstrating that tungstate is indeed more conducive to the transfer of energy to Eu³⁺ions than molybdate.When the doping ratio of Dy³⁺and Eu³⁺is 1:2,the color coordinates（0.324,0.323）of SrWO₄:Dy³⁺and Eu³⁺are close to the international standard white color coordinates（0.330,0.330）,indicating that SrWO₄:Dy³⁺,Eu³⁺phosphor may be A potentially very good white LED white phosphor.However,SrMo O₄ phosphors have weaker energy transmission from the molybdate to the luminescent center and are affected by the blue light of the substrate itself.When the ratio of the amount of the substances Dy³⁺and Eu³⁺is 1:2,the luminescence intensity of the phosphor reaches the maximum,the color coordinates To be inferior to the color coordinates of the SrWO₄ phosphor.（3）The Eu³⁺and Tb³⁺co-doped CaWO₄ and CaMoO₄ phosphors were prepared by microwave method without adding active agent.Under the excitation of 393 nm,the emission peak intensity of the two phosphors increases with the proportion of Eu³⁺in the total doped ions.A series of narrowband excitation peaks and overall emission peaks of CaWO₄ between 350-410 nm are much stronger than those of CaMoO₄phosphors,especially the characteristic transitions of Eu³⁺are stronger at 393 nm and 616 nm.This shows that the energy transfer from tungstate to Eu³⁺ion is more prominent than molybdate.When the ratio of Tb³⁺and Eu³⁺substances is 1:2,the best color coordinate of CaMoO₄（0.340,0.325）is very close to the standard white color coordinates（0.330,0.330）.This Eu³⁺,Tb³⁺co-doped CaMoO₄ phosphor has application potential in the field of white LEDs.