Study On Preparation And Properties Of Er³⁺: PbF₂ Transparent Ceramic

Lead fluoride is a excellent comprehensive performance Cherenkov material for its high density,high refractive index,short radiation length,and high ultraviolet transmittance.Lead fluoride crystal or lead glass are applied in the high-energy physics reserch in the past,but the crystal's production is high cost and difficult to grow large size materials,composition segregation occurring at high doping concentration.lead glass have disvantage in thermal conductivity.Those shortcomings limit the wide application of lead fluoride.But the ceramic has the advantage of preparation technology and better physical properties,This paper considers the application of polycrystalline transparent ceramic with lead fluoride matrix to replace single crystal in high energy experimental field.On the other hand,the low phonon energy of fluorine ions makes the non-radiative transitions of doped rare earth elements less,it can obtained better quantum efficiency than oxide.In this paper,the preparation of rare earth doped lead fluoride transparent ceramics and the research on the properties of up-conversion were carried out.In the first part,The synthesis process and sintering properties of pure PbF₂,Y³⁺:PbF₂?Er³⁺:PbF₂ nanopowder were studied.PbF₂ nanopowders were synthesized by precipitation method and hydrothermal method,Y³⁺:PbF₂nanopowders and Er³⁺:PbF₂ nano powder were synthesis by coprecipitation method,and the XRD diffraction,differential thermal analysis,scanning electron microscope and IR spectra test methods were used to characterize the prepared powder.The results showed that the reaction concentration had different effects on the phase composition,morphology and particle size of the powders.The size of orthorhombic lead fluoride powders preparated by precipitation method is 80 nm,with well dispersed,the size of cubic lead fluoride powders preparated by hydrothermal method is 35 nm,with obvious aggregation.The 1 at.%Y³⁺-doped cubic phase nanopowders were synthesized by co-precipitation method,the particle size is 25 nm,with some aggregation.Er³⁺-doped fluoride nanopowders was synthesized by co-precipitation method,with doping concentration increased from 1 at.%to 20 at.%,particle size decrease from 30 nm to 20 nm,with agglomeration increase.The optimum process is positive titration,5 at.%doping concentration,the average grain size of nanopowders is 25 nm,the powders is well dispersed and sintering performance is the best.The effect of calcination on cubic and orthorhombic PbF₂powder were analyzed.In the second part,the ceramic of pure PbF₂,Y³⁺:PbF₂ and Er³⁺:PbF₂ were preparated and the optical properties were studied.The effects of different titration method,doping concentration of rare earth and sintering temperature on the microstructure and transmittance of ceramic were studied.The sintering process of PbF₂ transparent ceramics was obtained,and the process parameters were sintering at 600?,last for 1 h,30 MPa pressure.Y³⁺:PbF₂ and Er³⁺:PbF₂ transparent ceramics were preparated by the sintering process and there isn't obvious pores or impurity microstructure,the transmittance of 2 mm samples at 1200 nm reached 65%and 73%,equivalent to 75%and 84%of lead fluoride crystal's theoretical transmittance,respectively,UV absorption edge near to300 nm.The 978 nm laser excitation of Er³⁺:PbF₂ transparent ceramics,in the range of visible region exists two high intensity of light emission spectral bands,535nm⁵60 nm?green?,650 nm⁶75 nm?red?,corresponding to the ²H_11/2,⁴S_3/2?⁴I_15/2and ²F_9/2?⁴I_15/2 radiation transition,respectively,and the intensity of red light was stronger than green light.To sum up,the Y³⁺:PbF₂ transparent ceramics prepared by hot pressing in this paper provides a new choice of Cherenkov material.Er³⁺:PbF₂ transparent ceramics prepared by hot pressing method,paving the way for the exploration of new optical materials.