YF3和PrF3共掺杂SrF2陶瓷的显微结构与光谱特性OA北大核心CSTPCD

Introduction The lattice environment of low phonon energy of strontium fluoride can suppress the energy loss caused by non-radiation process of trivalent lanthanide ions,so it is an ideal matrix material for active-ions doping.The fabrication and spectroscopic properties of SrF2 transparent ceramics doped with trivalent lanthanide ions have attracted recent attention.Trivalent lanthanide ions tend to form clusters in SrF2 crystal lattice,and the distance between ions shortens,resulting in energy exchange process and concentration quenching within these clusters,especially for rare-earth ions with a rich energy level structure.The concentration quenching effect leads to a reduction in luminescence intensity,and their applications are limited to a certain extent.Co-doping buffer ions into Pr∶SrF2 system is an effective solution to alleviate the concentration quenching of Pr3+luminescence intensity.In this paper,Y3+ions were selected as buffer ions.SrF2 raw powder was synthesized by a chemical precipitation method,and Pr3+and Y3+ions co-doped SrF2 transparent ceramic were fabricated in vacuum by a hot pressing(HP)sintering technology.The effect of Y3+doping levels on the microstructure and luminescence spectroscopic characteristics of Pr,Y∶SrF2 transparent ceramics was discussed to regulate the luminescence properties of Pr3+in SrF2 transparent ceramics. Methods SrF2 particles were synthesized by a chemical precipitation method with commercial strontium nitrate and potassium fluoride reagents.Cationic(Sr2+)and anion(F-)solutions were prepared,and then separated via high-speed centrifugation after washing for three times.The as-synthesized SrF2 particles were mixed with commercial available PrF3 and YF3 particles,where the doping level of PrF3 was fixed at 3.0％and the level of YF3 was varied from 0 to 10.0％.Pr,Y∶SrF2 transparent ceramics were fabricated in vacuum by a hot pressing sintering technology.The sintering temperature was 1 000 ℃,the pressure was 30MPa and the holding time was 120 min.After the heat preservation,the ceramic samples were cooled to room temperature in the furnace,and the ceramics were polished on the both sides. The transmittance and absorption spectra of the ceramics were determined by a UV-vis-NIR spectrophotometer,and the phase composition of the transparent ceramics was characterized by a X-ray diffractometer.The polished transparent ceramics were immersed in 6 mol/L hydrochloric acid solution and corroded at room temperature for 10 min.The microstructure of transparent ceramics was measured by a phenom Prox model scanning electron microscope.The luminescence spectra and fluorescence lifetime of transparent ceramics were measured by a fluorescence spectrofluorometer. Results and discussion The diameter of Pr,Y∶SrF2 transparent ceramics is 16 mm and the thickness is 2 mm.The lattice parameters of ceramics are gradually decreased after Sr2+are replaced by the smaller Y3+.Pr,Y∶SrF2 ceramics co-doped with 0-5.0％YF3have the similar transmittance,and the maximum transmittance of the ceramics is close to 90％.The ceramic co-doped with 5.0％YF3has the maximum transmittance,and the transmittance at 400 nm wavelength is 90.1％,which is similar to the theoretical value.The transmittance of Pr,Y∶SrF2 ceramics decreases significantly with the increase of YF3 co-doping level to 10.0％. After YF3 co-doping,the absorption capacity of the ceramic is enhanced,and the strongest absorption capacity is located at 443 nm.The ceramic has a dense microstructure without residual pores or impurity phase.The lattice distortion caused by the radius difference between Y3+and Sr2+promote the diffusion rate of ions at a high temperature and increase the average grain size of ceramics.3P2 states of Pr3+are directly populated from 3H4 ground states under light excitation at 443 nm,and then fall back to adjacent 3P1,3P0 and 1D2 states through non-radiative relaxation,multiphonon relaxation and cross relaxation processes.These radiation transitions from generated high energy states to lower states forming different spectral bands.Y3+break the cluster structure of Pr3+,releasing more luminous centers,and reducing the energy transfer process within Pr3+,thus improving the luminous intensity.Y3+co-doping causes the change of the local coordination environment around Pr3+,varying the transition probability between different energy states.The increase of the transition probability corresponds to the increase of the emission intensity.The proportion of emission band intensity to the total luminous intensity of Pr,Y∶SrF2 ceramics varies with the co-doping levels of YF3,and the proportion of orange luminescence band intensity increases in the spectrum.The co-doping of Y3+ions leads to serious distortion of SrF2 lattice,decreases the symmetry of matrix structure,and accelerates the energy transition rate.The fluorescence lifetime of Pr3+energy transition decreases with the increase of Y3+co-doping level. Conclusions SrF2 particles were synthesized by a chemical precipitation method,and Pr,Y∶SrF2 transparent ceramics were fabricated by a hot pressing technique.The ceramic co-doped with 5.0％YF3 had the mximum transmittance,and the transmittance at 400 nm was 90.1％.As the co-doping level of YF3 increased to 10.0％,the transmittance of Pr,Y∶SrF2 transparent ceramics decreased,and the average grain size increased to 200.1 μm.The co-doping of Y3+ions into Pr,Y∶SrF2 transparent ceramics improved the absorption capacity of the ceramics.The absorption cross-sections of Pr∶SrF2 and Pr,Y∶SrF2 transparent ceramics at 443 nm were 3.59× 10-21cm2 and 1.13×10-20 cm2,respectively.The luminescence spectral properties of Pr,Y∶SrF2 transparent ceramics were regulated via changing the clusters and local coordination structures of Pr3+in the matrix,and the luminescence of the ceramics gradually changed from reddish to orange-yellow.The lifetime of 3P0→3H4,1D2→3H4and 3P0→3F2transition decreased from 114.2,100.4 μs and 91.8 μs to 28.6,24.4 μs and 30.3 μs,respectively.