Preparation And Study On Luminescent Properties Of Ca₂LaZr₂Ga₃O₁₂ System Rare Earth Luminescent Materials

Phosphor converted white light-emitting diodes(W-LEDs)with high efficiency,long lifetime,energy conservation,environmental protection as well as other advantages are experiencing rapid development,which results in the great changement in lighting industry.At this stage,one of the solutions to obtain high brightness light is combining the blue light emitted by LED chip with the yellow fluorescent powder that can be excited by LED chip.However,the white light faces the problem of lacking red component leads to a low color rendering index,and thus additional red phosphors must be introduced to achieve high color rendering index.An alternative way of the combination of near ultraviolet LED chip with red,green and blue phosphors is proposed to realize high quality white light.Since ultraviolet light is invisible to the human eye,the white light obtained by this implementation is color stable.However,there is still a lack of qualified red phosphors,which limits the application of white LEDs.Therefore,it is that important to develop red phosphors with stable physical and chemical properties,that can be effectively excited by ultraviolet light,for improving the comprehensive performance of W-LEDs.This paper focuses on the Eu³⁺,Tb³⁺/Eu³⁺and Bi³⁺/Eu³⁺activated garnet structure Ca₂La Zr₂Ga₃O₁₂(CLZG)phosphors.The luminescence properties and the thermal stabilities are discussed in detail.The major results are as following:1.The series of CLZG:Eu³⁺samples were prepared by high temperature solid state reaction.The luminescence properties were studied by steady-state spectroscopy.The emission intensity of CEZG with the strongest emission intensity in CLZG:Eu³⁺series samples was compared with that of commercial phosphor Y₂O₃:Eu³⁺.It was found that CEZG had stronger red emission.Moreover,the temperature dependent emission spectra were also carried out and the results indicate the sample with a good thermal stability.2.The series of CLZG:Tb³⁺,Eu³⁺samples were prepared by high temperature solid state reaction.The luminescence properties were studied by means of steady state spectroscopy.The energy transfer process of Tb³⁺?Eu³⁺was also analyzed.With the increase of Eu³⁺doping concentration,the intensity of Tb³⁺green emission located in 543 nm decreases gradually accompanied by the increase of the intensity of Eu³⁺red emission.The emission color can also turned from green to red by adjust the ratio between Tb³⁺and Eu³⁺.The chromaticity coordinates can be changed from(0.2762,0.5981)to(0.5432,0.4026).In addition,the decay curves of Tb³⁺green emission under 371 nm excitation were measured,the energy transfer efficiencies of Tb³⁺?Eu³⁺were also calculated.The energy transfer efficiency of Tb³⁺?Eu³⁺can reach 86%at the doping concentration of Eu³⁺is 0.3.3.The series of CLZG:Bi³⁺,Eu³⁺samples were prepared by high temperature solid state reaction,and the energy transfer process of Bi³⁺?Eu³⁺was analyzed by steady-state spectroscopy.And it turns out that the mechanism of energy transfer is dipole-dipole interaction.The energy transfer efficiency of Bi³⁺to Eu³⁺was calculated by the luminescence intensity,which was as high as 99%.It shows that Bi³⁺transfers energy to Eu³⁺is very efficient.