Preparation And Luminescent Properties Of The Rare-earth Doped Mineral Structure Phosphors

In recent year,luminescent material is extensively applied in lighting,display and communication,the Rare-earth doped mineral structure luminescent materials have received great attention in their component and structure.As the new light source,white light emitting diode?WLEDs?has many advantages,such as economical and high efficiency,long service life and environmental protection.The commercial way to get WLEDs is combining a blue InGaN LED chip with Y₃Al₅O₁₂:Ce³⁺(YAG:Ce³⁺)yellow phosphor.However,such WLEDs have low color rendering index and high correlated color temperature due to the lack of red light,which limited its application.WLEDs are also made with near-ultraviolet LED chip excitated tricolor phosphors?red,blue and green phosphors?,which has high color rendering index and stable luminescence properties.It is well known that the matrix structure of luminescent materials has an important influence on the luminescent properties,structure regulation is one of the important methods for obtaining single-phase polychromatic phosphors.The diversity of mineral structure and its chemical constituents provides more selectivity for the matrix structure regulation of luminescent materials.The use of the structural characteristic of mineral materials,crystal structure and coordination polyhedron configuration of minerals,the luminescent properties can be regulated by adjusting the matrix structure.Through the doping of activator ions and the crystal field environment of mineral structure luminescent materials,research the energy transfer process between different valence ions,and realize the luminescence spectrum regulation.Therefore,the study of luminescent material matrix based on mineral structure has important research significance and application value.In this paper,two kinds of mineral structure luminescent materials have been synthesized by high temperature solid state method,and the effects of different mineral structures on the luminescence properties have been studied.Part one,Research double perovskite AA'BB'O6 structure?LiLaMgWO6?,LiLaMgWO₆:Eu³⁺red phosphors were prepared by high temperature solid state method.The effects of different doping concentration of Eu³⁺on the structure and luminescence properties of LiLaMgWO₆ were studied,and the structure of LiLaMgWO₆ was calculated by structural refinement.The results show that the red phosphors with high brightness,high color purity,good thermal stability and high luminous efficiency have been prepared.Judd-Ofelt theory is used to study the lattice occupation of Eu³⁺ions in LiLaMgWO₆.The experimental results show that Eu³⁺occupies the asymmetric lattice site in the LiLaMgWO₆ lattice,and the luminescence increases with the increase of Eu³⁺ion doping concentration,the optimum doping concentration is 30%.At the same time,the mechanism of energy transfer and thermal quenching was studied to provide guidance for the preparation of other other structural types of phosphors.Part two,Research double perovskite AA'BB'O₆ structure?LiLaMgWO₆?,LiLaMg?W,Mo?O₆:Eu³⁺red phosphors were prepared by high temperature solid state method.The effects of B-site atom substitution(Mo⁶⁺doping)on the structure and luminescence properties of phosphors were investigated.The structure,energy band and density of states of LiLaMgW_1-xMo_xO₆ are obtained by structural refinement and first principles calculation.The results show that with the increase of the doping concentration of Mo⁶⁺,the UV absorption band appear red shift.The excited position of the charge transition state of LiLaMgW_1-xMo_xO₆ is matched to the emission of³80 nm of the commercial near ultraviolet LED chip.Finally,LiLa_0.8MgW_0.7Mo_0.3O₆:0.2Eu³⁺red phosphors with high brightness and high color purity were obtained,and the luminescent properties of packaged white LED devices were studied.Part three,Research double perovskite AA'BB'O₆ structure?LiLaMgTeO₆?,LiLaMgTeO₆:Mn⁴⁺far-red phosphors were prepared by high temperature solid state method.Its structure and luminescent properties were studied,and explore its influence on the far red light plant illumination.The results show that the phosphor has strong far red emission at 708 nm,and its stability is excellent thermal stability.Mixed with commercial blue and green phosphors,white LED devices are packaged,and the performance of the devices is analyzed.Part four,Research whitlockite?-Ca₃?PO₄?₂ structure?Sr₈MgLa?PO₄?₇?,Sr₈MgLa?PO₄?₇:Eu²⁺phosphors were prepared by high temperature solid state method.The structure and luminescence properties were studied.The broadband yellow emission from the 4f⁷?4f⁶5d¹ transition of Eu²⁺in 550 nm is obtained.The near-UV excited white LED phosphors with good thermal stability were obtained by temperature-dependent luminescence spectroscopy.