Preparations Of Eu³⁺Doped Phosphors With Perovskite Structure And Research On White Light-emitting Diodes

The luminescent properties of composite oxides with perovskite structures have been greatly researched and will have a board application prospect in future due to its characteristics,such as layer crystal structure,allowing a large number of ion substitution and rich crystal types.In recent years,it becomes a research hotspot for exploring structures and studying luminous performance for rare earth ions doped luminescent composite oxide with perovskite structure.Because of physical stability and high luminous intensity under the extreme environmental conditions,these materials will be suitable for application in the field of white light-emitting diodes?WLED?.Therefore,the double structure and four directions of tungsten bronze type of perovskite tantalum/niobate luminescent material have been prepared and results are listed as following:1.A new type of perovskite-type red light-emitting material SrAlRO₅:Eu³⁺?R = Nb,Ta?have been prepared by the solid state method at high temperatures.The structural properties of SrAINbO₅ perovskite type were analyzed by XRD diffraction and Rietveld refinement.According to the fluorescence spectrum analysis,SrAlNbO₅:Eu³⁺ can be excited by blue,green and ultraviolet light,respectively.The wavelengths of three kinds of lights are 465nm,530nm and 395nm,and the main emission transition is ⁴D₀?⁷F₂,which emits a narrow emission peak at 615nm.When Eu³⁺ content is 11 mol%,Eu³⁺ ions replace the Sr²⁺ and local at different lattice sites in the crystal of SrAlNbO₅:Eu³⁺.The distance between Eu³⁺ ions is 16.78A,and the energy transfer mode for the electric dipole-electric dipole.While the content of Al₂O₃ is 5mol%,the phosphor possess the highest luminous intensity,which color coordinate is?0.683,0.317?,and the color purity is better than that of the commercial red phosphor Y₂O₃:Eu³⁺.2.SrAlTaO₅:Eu³⁺ luminescent materials were fabricated by using of solid state method at high temperature.Under the 465 nm blue light excitation,the red emission with board peak can be observed which located at 615 nm.Activator Eu³⁺ ions are located in the asymmetry of Sr²⁺ ions lattice site in the unite cells,which was formed by ⁷F₂ energy level splitting into ⁷F_3/2 and ⁷F_5/2 two energy level.The color coordinates were analyzed to be?0.685,0.685?and it is indicated that the color purity is better than that of commercial available Y₂O₃:Eu³⁺ phosphors.3.The tetragonal tungsten bronze perovskite structure composite oxide of Sr_2.83Ta₅O₁₅ was obtained by covering method.The effects of different proportions of ZnO on luminescence properties and the structure of Sr2,83Td5O15:Eu³⁺ were investigated.Fourier transform infrared spectroscopy?FTIR?shows that the introduction of ZnO would reduce the Ta-O octahedron in the crystal,and Zn²⁺ ions can also replace the Ta²⁺ions at the B position.Using the fluorescence spectrum analysis,it was found that the spectrum peak will shift to blut with the increase of ZnO doping amount.When the ratio of Ta and Zn is to be 9:1 and content of Eu³⁺ is 20mol%,the luminous performance of the sample will be reached to be best.The orange light emited at 395nm was generated by blend excitation with 592nm and 615nm.CIE color coordinates can be obtaind with?0.638,0.355?.The formula of Sr_2.77Ta_4.5ZnO₁₅ was determined by XRD analysis,and the substitution mechanism of Zn²⁺ was also analyzed.4.The mixing phosphors were modulated for application for blue emitted chip and ultraviolet emitted chip of white light-emitting diodes.When mixing ratio of 1:3 between SrAINbO₅:Eu³⁺ red phosphors and commercial available of YAG:Ce³⁺ yellow phospho,it gets high quality white performance on blue chips.For the UV chip LED,the Sr_2.77Ta_4.5ZnO₁₅:Eu³⁺ orange phosphor was mixed with the prepared Sr₄Al₁₄O₂₅:Eu³⁺ green phosphor and PCL:Eu²⁺ blue phosphor,and the ratio among red,green and blue was reached to be 8.45:1:0.95,the white light-emitting diodes with cold white color were obtained when exciting at 395nm.