Study On Hydrothermal Synthesis、Luminescence And Temperature-sensitive Properties Of Several Rare Earth Fluorescent Materials

Rare earth luminescent materials have special physical and chemical properties due to the unique electronic configuration of rare earth elements,which is the object of extensive research by researchers.They can be made to emit light by different means such as electricity,light and heat,the light emitted is bright in color.At present,rare earth luminescent materials play an important role in various fields,such as daily lighting,white LED,fluorescence thermometer,LED display,temperature sensing,biological imaging,etc.Although many applications and properties have been explored,they still have great development potential and research value.We know that the substrate of rare earth luminescent materials is particularly important,because it determines the lattice environment of rare earth ions,which directly affects the final performance.Researchers at home and abroad have studied most of the matrix materials based on borate,silicate,molybdate,fluoride,etc.Molybdate has good physical and chemical stability,and high color purity,while fluoride has the advantages of low lattice phonon energy,high energy transfer efficiency,long fluorescence life,etc.In view of this,these two matrix materials have been concerned.In order to find an efficient rare earth luminescent material,in addition to the selection of substrate,doped rare earth elements also need to be considered.We often use sensitizer ions and activator ions co-doped to improve luminescence efficiency.However,lanthanide elements are difficult to purify,and the cost is high.the environmentally friendly and low-cost main group elements such as Sb³⁺and Bi³⁺may be a better choice.The main research contents of this paper are as follows:（1）Three kinds of nanocrystals,AgBi（MoO₄）₂,Sr₂GdF₇ and Ba₄Yb₃F₁₇,were synthesized by a simple hydrothermal method.By changing various experimental conditions,such as pH value,doping ions,additives,fluorine source and material ratio,the crystal microstructure was adjusted to obtain rich morphologies.Their phase structure and morphology were analyzed by X-ray diffraction,field emission scanning electron microscope,transmission electron microscope and other characterization methods.The emission intensities of Ba₄Yb₃F₁₇:Eu³⁺crystals with different morphologies were also compared and explained in combination with the microscopic growth mechanism of crystals.（2）By doping rare earth ions(Yb³⁺,Er³⁺,Ho³⁺,Tm³⁺,Ce³⁺,Tb³⁺,Eu³⁺,etc.)in the matrix material,a series of phosphors with rich luminescence color were obtained.By adjusting the concentration of dopant ions in AgBi（MoO₄）₂:Yb³⁺/Ho³⁺/Tm³⁺phosphors and Ba₄Yb₃F₁₇:Ho³⁺/Tm³⁺phosphors,the up-conversion white light emission consistent with the international standard chromaticity coordinates is achieved.In addition,the energy transfer phenomenon and mechanism between doped ions in different substrates are also studied.（3）Using the dependence of fluorescence intensity ratio on temperature,the fluorescence intensity ratio of AgBi（MoO₄）₂:Yb³⁺/Er³⁺phosphors in the temperature range of 323-523K was studied.The fluorescence intensity ratio of two thermally coupled energy levels(²H_11/2 and ⁴S_3/2)varied with temperature.According to the Boltzmann distribution,it is found that the maximum sensitivity of AgBi（MoO₄）₂:Yb³⁺/Er³⁺phosphor is 1.32K^-1 at 463K.Compared with other fluorescent temperature sensing materials,it shows excellent thermal sensing performance.