Study On The Preparation And Spectral Properties Of Nd,La:Sr F₂ Transparent Ceramics

Laser technology is an indispensable supporting technology in 21st century,which has been widely used in civil and military fields.Laser gain medium is the foundation and core of the development of laser technology.Among them,transparent ceramics have rised wide attention in the field of solid-state lasers in recent years due to their advantages of being able to be prepared in large size,high doping concentration and good thermal and mechanical properties and so on.SrF₂ transparent ceramics are suitable to being a matrix material for laser gain medium because of its excellent properties of low phonon energy and refractive index,wide transmission range,no birefringence effect and short preparation period and so on.Nd³⁺ions are common active ions in solid-state lasers for its abundant energy level structure,wide absorption band,large absorption and emission cross section,long upper level lifetime and so on.However,the cluster of Nd³⁺ions is serious,which is prone to concentration quenching,leading to the decrease of fluorescence intensity and fluorescence quantum efficiency of laser ceramics.In this paper,we try to obtain better spectral properties by co-doping buffer ions La³⁺ions.In this paper,Nd,La:SrF₂ nanopowders doped with different content of La³⁺ions were synthesized by chemical precipitation method,and corresponding transparent ceramic samples were prepared by vacuum hot pressing sintering method.The effects of the doping La³⁺ions on the spectral properties of nanopowders and ceramic samples were systematically studied.The main research contents are as follows:1.Nd,La:SrF₂ and Nd,La:CaF₂ nanopowders were synthesized by chemical precipitation method.The effects of La³⁺ion on grain size,lattice parameters and microstructure were investigated.The results show that the average grain size of Nd,La:SrF₂ nannopowder decreases from 28 nm to 22 nm with the increase content of La³⁺ions,while the lattice parameters present an upward trend.But the increase of lattice parameters of CaF₂ is obviously after the doping of La³⁺ions,while that of SrF₂ is more obvious at higher content of La³⁺ions.In addition,in this experiment,LaF₃ impurities appeared when La³⁺ions doped with 21 at.%.2.Nd,La:SrF₂ transparent ceramics were prepared by vacuum hot pressing sintering method.The optical quality and spectral properties of ceramic samples were studied.It was found that the optical quality of ceramic samples was better,through preparing by sintering for 2 h with nanoparticles with better uniformity and dispersity of particles as raw materials,whose transmittance at 1056 nm reached to 88.04%.The results of spectral properties show that La³⁺ions have a modulated effect on the spectral properties of Nd,La:SrF₂ transparent ceramics.It can not only broaden the linewidth of absorption peaks and increase the intensity of absorption peaks,which is beneficial to LD pumping,but also break the serious concentration quenching cluster of Nd³⁺ions and increase fluorescence intensity and fluorescence lifetime.3.Nd,La:SrF₂ and Nd,La:CaF₂ transparent ceramics were prepared by vacuum hot pressing sintering method.Their emission spectral performances and lifetimes were studied and compared.It is found that the emission spectral properties of the SrF₂ transparent ceramics with the same doping content are better than that of CaF₂transparent ceramics for its higher emission intensity.However,La³⁺ions plays a greater role in modulating the spectral properties of CaF₂ transparent ceramics for its greater increments of emission intensity and degree of shift of the emission peak.