Preparation And Properties Of Rare Earth Doped Gadolinium Oxysulfide Luminescent Materials

Since commercial LEDs of YAG:Ce3+ phosphors(Ra<70 and CCT>6000 K)have lower color rendering and higher color temperatures,there is an urgent need to develop new LED materials with better performance.In recent years,the red,green,and blue phosphors excited by the ultraviolet-near ultraviolet LED chips become The current research focus of LED material research workers.Based on this situation,this article uses a very stable sulfur yttrium oxide as a substrate by high temperature solid-state,through the doping of erbium and europium as an activator,a series of high-temperature solid-state phosphors have been successfully synthesis,and the crystal structure and luminescent properties of phosphors have been studied.A detailed analysis was performed and the phosphor color of the phosphor was adjustable.It is best to use the best sample and near-ultraviolet InGaN chip to make white LED devices,and to characterize the optoelectronic performance of white LEDs.The specific research content is as follows:(1)Gd2O2S:Tb3+ micro/submicro crystals were prepared by high temperature solid phase method and the effects of reaction conditions on the crystals'growth and its luminescence properties were investigated.The Gd2O2S:Tb3+ powders were characterized.The main characterizations were field emission scanning electron microscopy(FE-SEM),high-resolution transmission electron microscopy(HRTEM),X-ray powder diffraction(XRD)and fluorescence spectroscopy(PL).,the results obtained show that each factor such as reaction time,temperature and Tb3+ doping quantity in the Gd2O2S:Tb3+crystals' growth et.al.has obviously effect on the luminescence properties.The sample doped with 7%of Tb3+,which was synthesized at 900? for 4h has the optimal fluorescence performance.The Gd2O2S:Tb3+ synthesized as above has excellent luminescent properties:a strong emission peak at ?=544nm appears when the crystals were excited by ?=254 nm light,which corresponds to Tb3+(5D40?7F5)transition.(2)Gd2O2S:Eu3+ micro/submicro crystals were prepared by high temperature solid phase method and the effects of reaction conditions on the crystals' growth and its luminescence properties were investigated.By means of characterization methods of field emission scanning electron microscopy(FE-SEM),the X-ray powder diffraction(XRD)and fluorescence spectroscopy(PL),the results obtained show that the sample doped with 7%of Eu3+,which the crystallinity and fluorescence intensity of the sample are the best.The phosphor is adapted to the preparation of a red LED.(3)In this work,the preparation,characterization,and photoluminescent mechanism of a Eu3+/Tb3+/Eu2+ coactivated Gd2O2S phosphor used for white-light emitting diode(W-LED)based on a near-UV chip are reported.Phase structure,morphology and composition of the resultant phosphors were characterized by X-ray diffraction pattern(XRD),scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).The luminescent properties of the phosphors were investigated by photoluminescence excitation(PLE),photoluminescence(PL)and decay lifetime.The energy transfer mechanism between different activator species in the Gd2O2S host was investigated in details.Importantly,the as-prepared Terbium/Europium co-doped Gd2O2S phosphors exhibited strong fluorescence with tunable color with the excitation of ultraviolet or visible light,whose excitation spectrum indicated that these phosphors can be effectively excited by ultraviolet light with the wavelength of 398 nm,matching well with the dominant emission band of a light-emitting-diode(LED)chip.After optimizing the preparation parameters,the phosphors doped with 10 at.%Eu and 0.7 at.%Tb can emit white color photoluminescence with coordinates of x = 0.3385 and y = 0.3195 in CIE chromaticity.The decay curves also exhibit that the lifetime of the phosphors can be effectively tuned from 0.55 ms to 1.10 ms.the present work suggests that these novel phosphors may have potential applications for white LEDs.