Study On Defect Regulation And Luminescent Properties In Haloapatite-type Compounds

Inorganic solid luminescent materials?commonly known as phosphors?are an important part of solid-state lighting devices.The luminescence properties of phosphors depend on point defects in the solid,including intrinsic defects and doping defects.Point defects break the periodicity of the crystal and generate defect levels in the solid energy band,significantly changing the local charge transition behavior.Therefore,reasonable design and effective control of point defects in crystals can obtain luminescent materials with certain luminescent properties.In recent years,the research on the control of luminescent properties of phosphors based on defect engineering has attracted widespread attention.The Haloapatite-type compound M₅?PO₄?₃X?M=Ca,Sr,Ba;X=F,Cl,Br?has excellent chemical stability,rich chemical composition and extremely high defect tolerance,which can be used as a good phosphor host material.In this paper,haloapatite-type compounds are used as the research object.By adjusting the atmospheric conditions and the solid solution components,the matrix defect luminescence of the phosphor and Eu²⁺doped long afterglow luminescence can be adjusted,and the dependence relationship between the crystal structure and intrinsic defect luminescence and the interaction between intrinsic anion vacancy defects and doped Eu²⁺defects are further explored,which provides new ideas for exploring new luminescent materials and realizing spectral regulation.1.Haloapatite self-activated phosphor and defect luminescence mechanism.Under reducing atmosphere conditions,the haloapatite compound M₅?PO₄?₃X?M=Ca,Sr,Ba;X=F,Cl?synthesized by high-temperature solid-phase method has self-activated luminescence properties.When X=Cl,the change of the emission color with M is continuously adjustable from blue to yellow,and it shows that oxygen vacancy?V_O?is the cause of the adjustable self-activated broadband emission in the visible region under short-wave ultraviolet excitation.When X=F,due to the higher concentration of F vacancy defects and the darker body color of the sample,only broad-band green light emission matching the spectral characteristics of oxygen vacancy defects is obtained in M=Ba.In order to study the photoelectric properties of the two types of anion vacancy defects,a series of PO₄-SiO₄ compounds were synthesized.Because SiO₄groups have high rigidity and low V_O defects,they exhibited near-ultraviolet excited blue light emission self-activated luminescence properties related to V_F defects.Using XRD,EPR,FT-IR and other characterization techniques,the dependence relationship between the formation energy of anion vacancy defects and crystal structure,and the structure-activity relationship of intrinsic anion vacancy defects and self-activated luminescence properties were thoroughly studied.2.M₅?PO₄?₃Cl:Eu²⁺phosphor and long afterglow properties.A series of M₅?PO₄?₃Cl:Eu²⁺solid solution phosphors were designed and synthesized based on energy band engineering to construct anion vacancy defects and Eu²⁺doping defects simultaneously in the chloroapatite matrix.The results imply that Ba₅?PO₄?₃Cl:Eu²⁺has a suitable trap depth,and uses anion vacancy defects as electron traps to make the phosphor have Eu²⁺long afterglow luminescence properties,but the afterglow life is short?<5s?.By forming a cation solid solution Ba_5-mCa_m?PO₄?₃Cl:Eu²⁺and Ba_5-nSr_n?PO₄?₃Cl:Eu²⁺make the afterglow life significantly longer.In addition,Eu²⁺in solid solution crystal occupies multiple cation sites at the same time,which broadens the emission spectrum,and the emission color is adjustable in the blue-cyan-green light range.Through the characterization of EPR and variable temperature spectroscopy,we propose that adjusting the proportion of solid solution components can adjust the trap depth and increase the trap concentration,thereby prolonging the afterglow time.3.Ba_5-mCa_m?PO₄?₃Cl:Eu²⁺,Ce³⁺long afterglow phosphor.In order to further extend the afterglow lifetime,the third defect center Ce³⁺was introduced,and a series of Ba_5-mCa_m?PO₄?₃Cl:Eu²⁺,Ce³⁺solid solution phosphors were synthesized.The results imply that by introducing Ce³⁺unequal substitution of Ca²⁺/Ba²⁺defects to create new electron traps,the afterglow performance is significantly improved.In addition,with respect to Ba₅?PO₄?₃Cl:Eu²⁺,Ce³⁺composed of endpoints,the solid solution phosphors extended the afterglow luminescence time by about 8 times to 8min.Combined with the variable temperature spectroscopy,TL,XPS and other tests,the number of traps generated after the introduction of Ce³⁺and the distribution of the traps of solid solution phosphor near room temperature were explored,and the long afterglow luminescence mechanism was proposed.