Preparation And Application Of Rare Earth Doped LiLuF₄ Micro And Nano Scintillator

Scintillation materials are widely used in national defense,nuclear medical imaging,high-energy physics,radiation therapy and other fields due to their ability to transform high-energy rays or high-energy particles into ultraviolet,visible light or current signals.Compared with traditional massive inorganic scintillation materials,inorganic micro-nano scintillation materials have many advantages,such as low synthesis temperature,simple preparation process,short preparation cycle,low preparation cost,convenient processing of flexible devices,etc.,and have attracted more and more attention in recent years.As a kind of matrix material with excellent optical properties,lithium lutetium fluoride（LiLuF₄）has an optically inert Lu³⁺ion,which can provide a suitable crystal field environment for rare earth doping.In addition,due to the stable chemical properties and low refractive index of LiLuF₄ crystal,it also has the potential of processing plasticity and organic compound application.Therefore,the design and preparation of new micro-nano scintillation materials based on LiLuF₄ matrix has significant research significance and value.In this paper,LiLuF₄ was used as matrix material,and high quality LiLuF₄nanocrystalline and microcrystalline materials were prepared by thermal decomposition method and hydrothermal method respectively.The scintillation properties of LiLuF₄nanocrystalline and microcrystalline materials were studied through rare earth doping modification strategy.In order to explore the application value of these materials,we developed the organic composite technology of micro-nano scintillation materials and successfully prepared the composite flexible scintillation film.In addition,the application potential of composite films in X-ray imaging is evaluated.The main work is as follows:1.LiLuF₄:Tb nanocrystalline was prepared by thermal decomposition method,and the doping concentration of Tb ion was optimized by comparing and observing changes in radioluminescence intensity.The results show that LiLuF₄:Tb nanocrystals have good X-ray cutoff ability,X-ray detection sensitivity and radiation damage resistance,and the detection limit is up to 36.3089 n Gy·s^-1.LiLuF₄:Tb nanocrystals doped with different rare earths also have adjustable multicolor luminescence properties.2.LiLuF₄:Tb,LiLuF₄:Tb,Cu and LiLuF₄:Tb,Pb microcrystals were prepared by hydrothermal method.The radioluminescence intensity of the microcrystals increased significantly after Cu²⁺or Pb²⁺co-doping.The X-ray response sensitivity and detection limit performance of LiLuF₄:Tb,Cu and LiLuF₄:Tb,Pb microcrystals were improved.It is found that the long afterglow performance of LiLuF₄:Tb microcrystals is further improved due to a large number of crystal defects caused by non-equivalent metal co-doping.In addition,the increase of deep defect levels makes the co-doped LiLuF₄:Tb,Cu microcrystalline materials exhibit X-ray energy storage characteristics.3.The preparation technology and imaging application of LiLuF₄ nanocrystals and LiLuF₄ microcrystalline polymer composite flexible films were explored.For LiLuF₄:Tb nanocrystalline material,a large area of inorganic nanocrystalline and epoxy composite flexible film was prepared by direct coating and in-situ polymerization after blending.The problem that nanocrystals tend to agglomerate was overcome and the high spatial resolution X-ray imaging application of 20 line pairs per millimeter(LP·mm^-1)was realized.For LiLuF₄:Tb and LiLuF₄:Tb,Cu microcrystalline materials,the composite flexible scintillation film was prepared by physical blending with polyacrylate and directly coating on PET substrate.The test results show that the spatial resolution of LiLuF₄:Tb composite film is 18 LP·mm^-1,and that of LiLuF₄:Tb,Cu composite film is 16 LP·mm^-1.In addition,LiLuF₄:Tb,Cu composite film also has the characteristics of X-ray optical information storage and thermal-luminescence imaging,which provides a new reference direction for X-ray multi-mode imaging.