Study On Synthesis,structure And Luminescence Properties Of Rare Earth Or Chromium Ions Doped Garnet-based Phosphors

In this thesis,a series of garnet structural phosphors doped with rare earth or chromium ions were successfully synthesized through high temperature solid-state reaction method.The synthesis,structure and persistence luminescence properties of the Ce3+and Yb3+ co-doped yttrium aluminum gallium garnet which can remain excellent stability and be efficiently excited by blue light,as well as luminescence properties of series of Cr3+ doped garnet compounds,were studied systematically in order to meet the requirements of different lighting applications.The main research contents and results are as follows:(1)The phosphor Y3Al2Ga3O12:Ce3+,Yb3+was successfully synthesized under various conditions,in order to study the effects of atmosphere,sintering temperature,sintering time and flux on the structure and afterglow properties.The afterglow property of the phosphor can be enhanced in N2 atmosphere with high pressure by appropriately reducing sintering temperature and time,and adding H3BO3 as flux.Then,a series of samples with different concentrations of B3+were synthesized under the optimal conditions.The incorporation of H3BO3 can improve the crystallinity,and also B3+occupies in tetrahedral sites,causing lattice contraction and modifying the trap depth and density.The charging process for persistent luminescence is demonstrated by comparing the photoluminescence excitation spectrum with the thermoluminescence excitation spectrum.The persistence luminescence mechanism is given by a visual energy level diagram on the basis of the vacuum referred binding energy scheme of Y3Al2Ga3O12.(2)A series of cationic-substituted Y3Al2Ga3O12:Ce3+,Yb3+,B3+ phosphors were successfully synthesized,including Si,Ge,Mg,Si-Mg,Ge-Mg,Si-Ca,Si-N substitutions.It was found that the phosphor obtained by non-equivalent substitution(Si4+ substituted for Al3+)had the best persistent luminescence performance.After that,a series of phosphors with different Si concentrations were prepared.The persistent luminescence duration has been dramatically enhanced over 40 h after visible light radiation,almost twice longer than the sample without Si4+.Moreover,the intensity of the persistent luminescence is also improved.The initial rise approach is used to demonstrate the exact trap distribution.Moreover,the potential applications in optical information storage of the phosphors are shown.At the end,we compared the effects Ce3+/Cr3+,Ce3+/Yb3+and Ce3+/Cr3+/Yb3+co-doping on the afterglow properties of Y3Al2Ga3O12:Ce3+phosphors,and found Ce3+/Cr3+co-doping is the best when the host is co-doped with B and Si.(3)We have designed and synthesized(CaYLu)(MgSc)(AlSiGe)O12:Cr3+luminescent phosphors and systematically studied their performances.The phosphor has a broad-band emission from 650 nm to 1100 nm with excellent luminescence thermal stability.A broadband NIR pc-LED is fabricated by coating the phosphor on a commercial 460 nm LED chip,The NIR pc-LED can be used as light source to measure transmission spectra of the palm and fnger,indicating the NIR garnet phosphor to be a promising candidate for biological imaging.Then,several groups of garnet compounds with different cationic were successfully prepared,and systematically studied in order to investigate the effects of different cationic ion types in the garnet matrix on the luminescence of Cr3+.This research opened a new chapter in the exploration of Cr3+ doped NIR phosphors.