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Synthesis And Luminescence Properties Of White Long-lasting Phosphors

Posted on:2013-06-26Degree:MasterType:Thesis
Country:ChinaCandidate:M H HeFull Text:PDF
GTID:2231330371483673Subject:Materials science
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Long-lasting phosphors is widely used in several fields because of its charactersof energy savings and environment protection. With the gradual research onlong-lasting phosphors, the research of the monochromatic light is so much. In thispaper,we synthesize different matrix and activators of white long-lasting phosphorswhich according to the principle of complementary light on the basis of themonochromatic light.In this paper,after careful study on the influence of doped rareearths on the luminescent property of long-lasting phosphors, the thesis synthesizeswhite phosphors with excellent luminescent property under the application ofdifferent experimental methods. The author of this thesis not only explores theinfluence of temperature, time, solvent, milling media and so on about luminescentproperties, but also adopts different characterization methods, such as X-raydiffraction (XRD), Scanning electron microscopy (SEM), fluorescence spectrum (FL),decay afterglow, IR and so forth, to analyze the structure and performance ofphosphors.The thesis consists of five sections: Introduction, experiment andcharacterization, analysis and discussion of white long-lasting phosphors synthesizedthrough high temperature solid state method, analysis and discussion of whitelong-lasting phosphors synthesized through gel-combustion method and conclusions.There is a detailed introduction about luminescent materials in the first chapter,including its definition, types, application and so forth;and also the research system,synthetic methods, applied area and luminescence principle of long-lasting phosphorsare described in detail; Based on these, the introduction also briefly introduces thestudy on white long-lasting phosphors, basis of topic selection and researchsignificance. The experiment and characterization as the following two parts of theexperimental basis introduce the raw materials, experimental equipments and themethods of characterization in detail.Taking Eu2O3, SiO2, Mg2(OH)2CO3,SrCO3,HBO3as the raw materials, whitelong-lasting phosphor is synthesized through employing the high temperature solidmethod, with Sr2MgSi2O7as its matrix and Dy3+as its doped activator. The thesis alsoanalyzes the influence of different elements on the long-lasting phosphor’sluminescent properties systematically, such as the doping content of Dy, the sinteringtemperature and time, the milling way, the addition of the cosolvent and so forth.After the experiments, we discover that the doping content of Dy will directlyaffect the luminescent property. Only in a certain doping concentration can theluminescence happen, and only in a certain sintering temperature and time can thephosphor with good luminescent property be synthesized. Different milling methodsalso has a certain impact on the luminescent properties. Moreover, the addition ofcosolvent will directly influence the sintering temperature and time, and therebyaffects the luminescent properties.Through different experimental characterization, we find that the excitationpeak of phosphor is the strongest under350nm, and the emission peak at this time isaround470nm,490nm,575nm and680nm.The combination of the470nm and490nmblue emission correspongding to the4F9/2â†'6H15/2transition,the575nm yellowemission correspongding to the4F9/2â†'6H13/2transition and the680nm red emissioncorrespongding to the4F9/2â†'6H11/2yielded white-light emission about thecharacteristic intra-configurational4f emissions of Dy.The complementary light givesoff white light which has the characteristics of high glowing brightness and longafter-glow time. However, the particle size of the powder is too large when using theSEM to analyze it.The white long-lasting phosphor SrAl2Si2O8:Eu2+,Dy3+is synthesized by takingthe gel-combustion method under a comparatively lower temperature. Throughanalysis under different experimental condition, its crystal structure and internalimpurities is measured by XRD, its spectrum property is determined through FL. The experimental results show that the doping content of Eu2+,Dy3+directlydetermines the luminescent property. Only when the doped content of Eu2+,Dy3+iscontrolled in a certain range can the luminescence happen. The ignition temperature,the amount of urea, the reduction temperature and time will all directly influence thecrystal structure of the sample, and thereby affect its luminescent property.The author of this thesis discovers that the excitation peak of SrAl2Si2O8:Eu2+,Dy3+is the strongest under270nm, when no cosolvent, its emission peak is around470nm and620nm; when cosolvent is added,its emission peak is around390nm,470nm,580nm and620nm.The390nm violet emission correspongding to the4H21/2â†'6H15/2transition of Dy,the470nm blue emission correspongding to the4f65d1â†'4f7transition of Eu,the580nm yellow emission correspongding to the4F9/2â†'6H13/2ofDy and the620nm red emission correspongding to the4F9/2â†'6H11/2transition of Dyand then the white light is synthesized. Through scanning electron microscopy (SEM)images, we find that the phosphor synthesized through gel-combustion method hasloose powder and is smaller in particle size with strong luminous intensity andafterglow property.The conclusion gives an overview of the previous four parts, including the mostappropriate synthetic condition of two luminous phosphors, the particle size, thespectrum property and so forth, and then concludes the whole thesis.In this paper, we synthesize different matrix and activators of white long-lastingphosphors which use high temperature solid state method and gel-combustionmethod,and its luminescent properties is so good that it can provided some theoreticalsignificance for white long-lasting phosphors.
Keywords/Search Tags:long-lasting phosphor, rare earth, high temperature solid state method, gel-combustion method, luminescent properties
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