ABSiO₄ And ?-Ca₃?PO₄?₂ Based Rare-earth Luminescent Material And The Investigation On Crystal Structure And Luminescence Properties

Rare earth luminescent materials are needed in the field of lighting,display,optical communication and detection.The research and development of high-performance rare earth luminescent materials is major national strategic needs.Among them,white light-emitting diodes?w-LEDs?for solid-state lighting are rapidly developing,and the phosphors are a key component and attract much attention.Our present work centres on the structural construction,preparation and photoluminesenc tuning in new rare earth luminescent materials for White LED.Based on the structural models ABSiO₄ and ?-Ca₃?PO₄?₂,the research on the structure modulation,color-tunable and preparation of several typical rare earth doped luminescent materials have been reported.The main contents are as follows:?1?The structural phase transformation of Ca2-xSrxSiO₄:Ce³⁺ phosphor can occur through Sr²⁺ substituting for Ca²⁺ in Ca₂SiO₄.The crystal structures of Ca2-xSrxSiO₄:Ce³⁺ are divided into two groups ? phase and a' phase,and the phase transition????'?mechanism has been revealed.The relationship between structural transformation and luminescence properties were analyzed in detail.?2?Through the cosubstitution of[Na+-OH-]for[Ca²⁺-02-]couple in Ca₂SiO₄,it can transform to the new phase NaCaSiO3OH.The hydrothermal methods can be developed to prepare NaCaSiO3OH particles,and the shape and size of NaCaSiO3OH particles mainly depend on the added ratio of solvent and water.The as-prepared NaCaSiO3OH can be in-situ transferred into Na₂Ca₂Si₂O₇ by the heat-treatment.The luminescence properties of Eu³⁺/Tb³⁺ doped NaCaSiO3OH and Na₂Ca₂Si₂O₇ microstructures are comparatively investigated,and the luminescent colors of Na₂Ca₂Si₂O₇:Tb³⁺,Eu³⁺ can be adjusted from green to yellow to red depending on the energy transfer of Tb³⁺?Eu³⁺.?3?Based on the research of BaO-SiO₂ phase diagram,the structural relationship between Ba4Si6O16 and Ba2Si3O8 has been investigated comparatively.Based on the the high-efficiency energy transfer of Ce³⁺-Eu²⁺ in the Ba4Si6O16 host,the emission colors of Ba4Si6O16:Ce³⁺,Eu²⁺can be tuning from blue to yellow.?4?A isostructural solid solution xSr₂Ca?PO₄?₂-?1-x?Ca10Li?P04?7:O.03Eu²⁺with ?-Ca₃?PO₄?₂-type structure has been designed and prepared.The mechanism of structural transformation and occupied rates of cations(such as Ca²⁺,Sr²⁺ and Li+)in each site have been investigated in detail.It is found that with the increasing of x.the local environment surrounding Eu²⁺ ions changed obviously,which can cause different luminescent behaviors corresponding to color-tunable?blueviolet?greenyellow?.?5?The occupation of activator and luminescent properties in the Ca10M(?PO₄?₇:Eu²⁺?M=Li,Na and K?phosphors with ?-Ca₃?PO₄?₂-type structure have been investigated.Based on the different cations?Li,Na and K?on the structure,the occupied situation of Eu²⁺ ions in different sites of Ca10M(?PO₄?₇?M?Li,Na and K?host has also been studied and explored.It is found that there are two emission bands?410 nm and 466 nm?are attribute to that Eu²⁺ occupy different cation sites,which result in different local environment surrounding Eu²⁺.