Fabrication And Optical Properties Modulation Of Praseodymium Doped Strontium Fluoride Transparent Ceramics

With the development of science and technology,there is an increasing demand for the research and application of new materials.As a new type of inorganic non-metallic material,transparent ceramics have inherent characteristics of ceramics such as high strength,high hardness and corrosion resistance.Transparent ceramics also have optical properties similar to glasses,and their unique properties and proven craftsmanship have attracted a great of attention.Strontium fluoride（SrF₂）has a phonon energy of only 280cm^-1,which is greatly reducing the polyphonon relaxation rate of rare earth ions(Re³⁺)and improving the quantum efficiency of the luminescence.In addition,SrF₂ has a high heat conductivity（9.3 W/（m·K））and wide range of light transmission,making it an excellent performance transparent ceramic matrix material.In this paper,SrF₂ was chosen as a substrate for Pr³⁺ion-emitting materials and transparent ceramics were fabricated by a vacuum hot-pressure sintering technique.The luminescence of transparent ceramics is regulated by co-doping of modulated ions and selection of near-infrared excitation sources to suppress the concentration quenching of Pr³⁺ions in SrF₂ transparent ceramics.The main research of this thesis are as follows:（1）SrF₂ powders were synthesized by chemical precipitation method,and Pr F₃powders were mixed.Pr:SrF₂ transparent ceramics were fabricated by vacuum hot-pressure sintering.The effect of Pr³⁺doping on the microstructure,transmittance and luminescence of the transparent ceramics were studied,and the sintering temperature of the transparent ceramics was optimized to obtain the optimal doping concentration and sintering temperature of Pr³⁺.（2）To improve the luminescence properties of Pr:SrF₂ ceramics,the La³⁺ions were selected as the modulating ions co-doped into the Pr:SrF₂ transparent ceramics.Pr,La:SrF₂ transparent ceramics were fabricated by vacuum hot-pressure sintering.Study of the effect of La³⁺-modulated ions on the light transmission and luminescence of Pr,La:SrF₂ transparent ceramics and the effect of sintering temperature on the densification and light transmission of ceramic samples（3）To enhance the absorption of the Pr:SrF₂ ceramic to the 980 nm excitation light source,Yb F₃ was co-doped into the Pr:SrF₂ transparent ceramic as a sensitizer.The effects of Yb³⁺ion concentration on the optical transmittance and microstructure of ceramics were investigated.The upconversion luminescence properties and energy transfer mechanisms of Yb³⁺and Pr³⁺ions in Pr,Yb:SrF₂ ceramics under 980 nm pumping are discussed.The results showed that the doping of Pr³⁺improved the optical transparency of Pr:SrF₂ transparent ceramics,and the transmittance of Pr:SrF₂ transparent ceramics doped with 3 wt.%Pr F₃ was 89.6%and 91.7%at 350 nm（visible）and 1200 nm（near infrared）,respectively.The optimal sintering temperature of Pr,La:SrF₂ transparent ceramics was 1050°C.The optimal doping amount of La F₃ was 1 wt.%the transmittance at 400 nm and 1100 nm was 87.8%and 87.2%.The co-doping of La F₃ significantly improved the emission intensity of Pr,La:SrF₂ ceramics and effectively suppressed the concentration quenching phenomenon in ceramics.Upconversion luminescence was achieved by doping Yb F₃ into Pr:SrF₂ ceramics and using a 980 nm light source in the near-infrared region as the excitation source.The optimal doping concentration of Yb F₃is 5 wt.%and the transmittance of the ceramic at the visible wavelength of 400 nm is85.6%.Upconversion luminescence in Pr,Yb:SrF₂ transparent ceramics is achieved by Yb-Pr energy transfer involving three-photon and two-photon luminescence mechanisms.The existence of a reverse energy transfer（ET）process from Pr³⁺to Yb³⁺ions was demonstrated.The sensitizer(Yb³⁺)plays a key role in the upconversion luminescence of Pr,Yb:SrF₂ transparent ceramics.