Fabrication And Characterizations Of Nd,Sr Co-doped CaF₂ Transparent Ceramics

Trivalent rare-earth ion doped CaF₂ host(Re³⁺:CaF₂)materials are of great interest for the development of laser systems.They are characterized by heterovalent substitution of Ca²⁺and different forms of charge compensation,resulting in a very broad and smooth absorption and emission spectra,which make it particularly suitable for the production of the amplification or ultra-short pulse lasers.It is very suitable for the ICF materials.Four-level neodymium?Nd?-doped have been proved as one of the most important laser ions at 1?m wavelength.In fact,A.Kaminskii has done extensive research about the spectrum and laser performance of Nd-doped CaF₂ single since1960s.However,Nd³⁺-doped CaF₂ materials as a laser system has been abandoned since a long time because of a concentration quenching effect which results from the clustering of the Nd³⁺ions and some cross-relaxation type energy transfers.In order to improve the optical properties of the Nd³⁺-doped CaF₂ materials,scientists have proposed a method by codoping the material with buffer ions such as M²⁺?Sr,Ba?or M³⁺?Y,La,Gd,and Sc?.In recent years,Sr²⁺doped CaF₂ crystal?CaF₂-SrF₂ mixed crystal?is widely studied for the development of efficient solid-state laser.However,compared with CaF₂-SrF₂ mixed crystal,fewer reports on CaF₂-SrF₂ ceramic have been published.T.T.Basiev et al.have reported optical properties and laser operation of CaF₂-SrF₂-YbF₃ nanoceramics by a hot-forming method.But,this method of CaF2-SrF2 ceramic preparation is based on the application of single crystals as raw materials.It lacks for some advantages of ceramic processing such as short manufacturing cycle and low fabrication temperature.In this study,the Nd³⁺:CaF₂-SrF₂ nanoparticles were synthesized by direct precipitation method.The influence of titration method,titration speed,Sr doping concentration and Nd doping concentration on structure,morphology and particle size Nd³⁺:CaF₂-SrF₂ nanopowders were investigated by XRD,FE-SEM and TEM.The results showed that the forward titration is better method for synthesizing nanoparticles.Titration speed has little effect on the sintering activity of nanpowders.Doping Sr has little effect on the particle size and morphology of the nanpowders.While it can reduce the crystallinity of the nanpowders.With the increase of Nd³⁺concentration,the grain size of the powder decreases and the morphology changes from the cubic to the spherical shape.Nd³⁺:CaF₂-SrF₂ transparent ceramics were fabricated by HP method.The results showed that 800? was preferred temperature.Nd³⁺:CaF₂-SrF₂ transparent ceramics with different Sr doping concentration were fabricated under 800?.The results showed that Sr has a modulation effect on the absorption and fluorescence spectra,which is related to the disordered structure produced by doping Sr²⁺.Nd³⁺:CaF₂-SrF₂transparent ceramics with different Nd doping concentration were fabricated under800?.The results showed that the transmittance,absorption and fluorescence spectra of Nd³⁺:CaF₂-SrF₂ transparent ceramics change with the Nd doping concentration change.