Investigation On Preparation And Properties Of Rare Earth Doped YAG Glass Ceramics

Rare earth ions doped luminescent glass ceramics that contain crystal luminescent materials have both the excellent luminescent properties and good physicochemical properties of the glass materials.It is expected to become an ideal luminescent matrix-material for LED,which can replace traditional fluorescent materials in the field of white light.Therefore,the composition design,luminescent properties and preparation technology of rare earth ions doped glass ceramics both are the research hot topics in this field in recent years.In this paper,Eu doped YAG glass ceramics was taken as research object,glass and glass ceramics was prepared by using melting method and two steps heat-treatment.Obtain appropriate preparation parameters by composition design;crystallization of YAG glass ceramics had been studied by using XRD,FESEM and DSC methods,and effect of Eu doping and doping concentration on microstructure and physical properties of YAG glass-ceramics had also been further studied;The effect of the excitation wavelength,heat-treatment conditions and Eu doping concentration on transmissivity,luminescence intensity and luminescence color of Eu³⁺and Eu²⁺of YAG glass ceramics had been studied and analyzed by the transmission spectrum,fluorescence spectrum and CIE coordinates.The results show that:（1）In the PbO-Y₂O₃-Al₂O₃-SiO₂ glass systems,the introduction of PbO could effectively reduce the melting temperature of glasses,compared with crown glass decrease,the melting temperature was reduced by 110²00℃,and the crystallization temperature of the pure YAG crystal was reduced by 280℃.When PbO/SiO₂=3.79,Al₂O₃/Y₂O₃=0.85（mass ratio）and the heat-treatment at 1100℃,the crystallization properties of YAG crystals in glass are better.In this composition system,glass was melting at 1420℃and then heat treated at 1050℃for 2 h,translucent glass ceramics that contain the pure YAG crystals was prepared,and the grain size of YAG was about40⁷5 nm.（2）The doping of Eu does not change crystalline phase precipitated in the glass,but with the increase of Eu doping concentration,the crystallinity of YAG crystals increases and the average particle size becomes larger.Eu enters into the YAG crystals would priority occupy the Y lattice,the lattice parameter become larger,but the doping of Eu does not cause the overall change in the crystalline structure of YAG.With the increasing of Eu doping concentration,the structure is more compact and the thermal stability is improved of glass and YAG glass ceramics.The effect of Eu doping on the refraction of the glass has little,and the refractive index of the glass before and after doping are about 1.92.（3）Under the UV-light radiation at any wavelength,the characteristic emission peaks of Eu³⁺and Eu²⁺in the Eu doped YAG glass ceramics can be obtained at the same time.Under the 335 nm radiation,the increase of heat-treatment temperature promotes the transformation of Eu³⁺to Eu²⁺,and the luminescence intensity of glass ceramics is continually increased.With the increasing of Eu doping concentration,the luminescence intensity of Eu²⁺is increased,and the luminescence intensity of Eu³⁺is first increased,then decreased,and the quenching concentration is 1.30¹.50 wt%.Finally,the Eu doped YAG glass ceramics with white light luminescence under the335 nm UV radiationn obtained when the Eu doping concentration is 1 wt%,and the coordinate is（0.3326,0.3005）.