The Study On Preparation And Scintillation Properties Of Eu²⁺ Doped CaF₂ Transparent Ceramics

Inorganic scintillator is one of the most widely used scintillator materials,mainly including ceramics,single crystal and glass.Compared with single crystal and glass scintillator,ceramics have some functions and advantages in preparation,such as high concentration doping,large size preparation,etc.Calcium fluoride matrix has the characteristics of high transmittance,band gap and low phonon energy,and has good application potential in the exploration of cosmic dark matter.Eu²⁺:CaF₂ single crystal has achieved high light yield and energy resolution.In this paper,Eu²⁺:CaF₂ powders were synthesized by co-precipitation method and Eu²⁺:CaF₂ ceramics were prepared by hot-pressing sintering.Eu²⁺,Y³⁺:CaF₂ powders and transparent ceramics were prepared by doping 1at.%Y³⁺and Eu²⁺ions with different concentrations.The main research contents are as follows:1.Eu²⁺:CaF₂ nano-powders were successfully synthesized by chemical co-precipitation method.XRD show that the powders synthesized were pure calcium fluoride phase,and the lattice constant decreases with the increase of doping concentration of Eu²⁺ions;SEM of the powders show that the powders tended to spherical shape with the increase of doping concentration of Eu²⁺ions,which enhance the sintering activity of the powders.The results of ICP measurements show the difficulty of substituting Ca²⁺with Eu²⁺increases with the increasing of Eu²⁺ions.2.Eu²⁺:CaF₂ transparent ceramics were successfully prepared by hot pressing sintering method.XRD show that no other impurities formed in the sintering process.SEM show that the grain size decreases and the inter-granular pore is less with the increase of Eu²⁺ion doping concentration.The transmittance spectra show that the transmittance of ceramics increases with the increase of Eu²⁺ion doping concentration,and the maximum transmittance is 7.23%at 425 nm.Under the excitation of 355 nm laser,the strongest emission peak appears at 425 nm when Europium ion doping is0.04at.%.3.When 1at.%Y³⁺ions were doped into Eu²⁺:CaF₂,the particle size of nano-powders decreased.The transmittance of 0.2at.%Eu²⁺,1at.%Y³⁺:CaF₂ ceramics at 423nm reach to 40.87%,which was 24 times higher than that of Eu²⁺:CaF₂ transparent ceramics.Y³⁺ions reduce the fluorescence quenching effect when the concentration of Eu²⁺ions is 0.2at.%and 0.5at.%with the strongest emission peak at 355 nm for 0.5 at.%Eu²⁺,1at.%Y³⁺:CaF₂ ceramics;Y³⁺ions inhibit the self-trapping exciton emission in calcium fluoride matrix,and increases the relative intensity of broadband emission peak at 422 nm wavelength.4.The pulse attenuation height and spectral decay curves of Eu²⁺:CaF₂ and Eu²⁺,1at.%Y³⁺:CaF₂ transparent ceramics with different concentrations show that the absolute photoelectron number of 0.2at%Eu²⁺:CaF₂ ceramics is 1230 pe/MeV and the scintillation decay time constant is 624 ns.The absolute photon number of photon yield decreases with the concentration increasing of Eu²⁺ions after doping with 1at.%Y³⁺ions.The absolute photoelectron number of 0.04at.%Eu²⁺,1at.%Y³⁺:CaF₂ transparent ceramics is 395 pe/MeV,and the scintillation attenuation time constant is 725 ns.The energy resolution of Eu²⁺-doped calcium fluoride transparent ceramics was measured for the first time.The energy resolution of 0.04at.%Eu²⁺,Y³⁺:CaF₂ transparent ceramics was the best with a value of 38.2%.5.When 1at.%Y³⁺ions were doped into 0.04at.%Eu²⁺:CaF₂,the thermoluminescence intensity increased significantly,and the shallow trap at the bottom of the conduction band shrank by about 0.69eV.The thermoluminescence intensity of co-doped samples increased with the increase of concentration increasing Eu²⁺ions,the defect distribution in the forbidden band increased,and the linear response sensitivity of 0.5at.%Eu²⁺,Y³⁺:CaF₂ ceramics is the best for irradiation dose.