| In the common luminescence research of solids doping,according to the luminescence law of different luminescent centers,it is often necessary to carry out the research on the properties and application based on the luminescence behavior of materials.This includes not only the research and development of novel luminescent materials,but also the design and optimization of luminescent schemes.In addition,in order to meet the different application requirements of luminescent materials,the improvement and precise regulation of luminescent performance of materials are also playing an increasingly significant role in the application of luminescent functional materials.Among the many luminescent active ions,rare earth ions and transition metal ions are the most common two types of luminescent centers in photoluminescence.On the one hand,when they are used as activation centers,they are an important basis for the study and analysis of various optical transition mechanisms in luminescent materials;On the other hand,as one of the most widely used inorganic luminescent materials,luminescent materials doped with rare earth ions or transition metal ions have prominent application prospects in many fields,such as solid-state lighting,backlit display,optical anti-counterfeiting,biomedicine,information storage,solar cells,detection sensing and so on.In this thesis,we chose the most representative europium ions(Eu2+,Eu3+)and manganese ions(Mn2+,Mn4+)as the research objects of active ion,and carried out the research on material preparation,spectral analysis,performance regulation and application exploration that must be experienced in the conventional application process in oxysalt system.In this way,the research ideas and theoretical methods used will provide some guidance and reference for the study of related luminescence direction.In general,the main content of the dissertation involves the regulation and optimization of luminescent properties in luminescent materials activated by europium ions or manganese ions,the development of new materials and new schemes,and so on.Taking the two as examples,the potential solutions to some problems in the fields of white LED and optical temperature sensing are proposed emphatically.Specifically,the main structure of this dissertation can be roughly arranged as follows:The first chapter is the introduction part of the thesis,which is to make a schematic understanding of the basic background of the research object.Firstly,we introduce some basic knowledge of luminescence,including the definition and classification of luminescence phenomena,the basic process of luminescence,the common characterization methods of luminescence and the commonly used configuration coordinate model.Secondly,some basic luminescence principles of the concerned rare earth ions and transition metal ions when they are used as luminescence centers are briefly described.Then,through the analysis of the factors affecting the luminescence,the angles or directions that can be considered when engaging in the regulation of the luminescence performance are grasped.Finally,the related application of luminescent materials is briefly introduced.The second chapter mainly introduces the structure and luminescence properties of Ba5-yCay(PO4)3Cl:Eu2+/Eu3+phosphors activated by europium ions.First of all,based on the abnormal spontaneous reduction of Eu3+→Eu2+phenomenon in the trivalent Eu3+ doped Ba5(PO4)3Cl material with apatite structure,the phase,structure and morphology of the material were understood by means of XRD and SEM.Secondly,the luminescence properties and reduction phenomenon of the materials were studied and verified by photoluminescence excitation or emission spectra,XPS and timeresolved spectroscopy.The analysis indicates that the adopted charge compensation model can explain the spontaneous reduction phenomenon qualitatively.Generally,the luminescent properties are largely determined by the material structure.Therefore,in the subsequent part of this chapter,we introduce Ca2+to perform solid solution cation equivalent substitution for the matrix components.After analyzing the regulation effect of this method on the luminescent properties in detail,we try to establish the relationship between the luminescent properties and the structure of the materials.Besides the method of cation substitution mentioned above,the energy transfer behavior during luminescence process is also a feasible way to control the luminescence properties of materials.In the third chapter,we study the luminescence enhancement and luminescence tuning properties of K2BaCa(PO4)2:[Eu2+,Si4+],Mn2+ phosphors around charge compensation and energy transfer.In general,the research content of this chapter can be divided into two parts.In the first part,by designing the charge compensation strategy of[Eu2+,Si4+]co-replacing the[K+,P5+]in the original material,it is surprising to realize the luminescence enhancement and thermal stability improvement(the luminous intensity is still 103%@548 K compared with room temperature)of the whole system.and the relevant mechanisms are also analyzed in detail.In the latter part of this chapter,based on the previous procedures of concentration optimization and charge compensation,we designed a luminescent system co-activated by Eu2+and Mn2+.By studying the luminescence properties of the materials and the energy transfer between Eu2+-Mn2+,the purpose of adjusting the luminescence properties of the materials was finally achieved.The research in the fourth chapter mainly focus on the investigation of the luminescence properties from a novel Mn4+-activated Sr2ScSbO6:Mn4+phosphor,and explore its potential for multi-field application.Specifically,a series of Sr2ScSbO6:xMn4+phosphors with different Mn4+ doping concentrations were prepared by the classical high-temperature solid-state method.The crystal structure,morphology and other properties of the materials were basically got acquaint by means of XRD,Rietveld refinement,SEM and XPS.In addition,the luminescent properties of the materials concerned were systematically understood combined with UV-vis diffuse reflection spectroscopy,photoluminescence spectrum and fluorescence decay curve.The results demonstrate that Sr2ScSbO6:Mn4+ material,which can be excited by near ultraviolet excitation light,has deep red emission at 698 nm with satisfactory color purity(91.77%).The research of thermal quenching behavior also reflects its excellent thermal stability.The above results show the application potential of the developed luminescent materials in the field of solid-state lighting.Therefore,its application prospect in indoor plant growth lighting is evaluated by comparing its emission spectrum with the absorption band of phytochrome.Furthermore,the spectral analysis at low temperature also manifests its application value in the field of optical temperature sensing.In recent years,red luminescent materials activated by transition metal Mn4+ ions and optical temperature sensing have attracted extensive attention.Generally speaking,the luminescence of transition metal Mn4+will be affected by temperature and have a very conspicuous luminescence thermal quenching,which limits its application in the field of solid-state lighting.On the other hand,for the scheme design of traditional optical temperature sensing,a widely used approach is to use the thermal coupling energy level in rare earth ions.This design principle also causes the limitations of low sensitivity and poor temperature resolution.In the fifth chapter,a fluorescence intensity ratio sensing scheme was designed based on the emission of transition metal Mn4+ ions and rare earth Eu3+ions by combining the above factors.It is confirmed the feasibility of the design scheme that the relative temperature sensitivity of the two phosphors up to 2.08%K-1 and 1.51%K-1 respectively after analyzing the optical temperature sensing results of A2LaNbO6:Mn4+,Eu3+(A=Ba,Ca)phosphors.It exploits the direction for the application of Mn4+and provides an innovative way for the scheme design of optical temperature sensing.At last,we present a summary and outlook of the main content briefly. |
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