Synthesis And Luminescence Properties Of Several Fluoride Luminescent Materials

Since fluoride luminescent materials have low phonon energy,low biotoxicity,high quantum efficiency and other advantages,they have a wide range of potential applications in LED devices,biological imaging,anti-counterfeiting encryption,solar cells and other aspects.Using fluoride Ba₅Al F₁₃,Na₃In F₆ and Na₂Mg Sc F₇ as matrix materials doped with transition metal ions Cr³⁺and some lanthanide ions,the purity,morphology,spectrum,stability and other related properties of the prepared phosphor samples were studied systematically.To provide theoretical and data support for the research and development of high-performance fluoride luminescence materials,the following three aspects are emphasized:（1）Ba₅Al F₁₃:Cr³⁺near-infrared luminescent materials were synthesized by hydrothermal method.Rietveld refinement revealed that its space group was Fd-3m,the cell parameters were a=b=c=17.364?,the cell volume V=5235.394?³.After doping,the cell parameters of the sample increased,where a=b=c=17.378?,cell volume V=5248.067?³.It is proved that Cr³⁺has successfully replaced Al³⁺.Under the excitation of 416 nm light,Ba₅Al F₁₃:Cr³⁺showed an emission peak of near infrared light at 712 nm with a full width at half-maximum of 94 nm.Combined with the fluorescence decay curve,it can be proved that there is only one emission center for Cr³⁺in the system.Additionally,the optimal doping concentration was 15%,when the temperature increases to 150℃,the emission intensity remained 66.7%of the initial value at room temperature,exhibiting excellent thermal stability.The obtained Ba₅Al F₁₃:Cr³⁺adaptive LED blue chip can be used to construct near-infrared LED devices.（2）Na₃In F₆:Cr³⁺,Yb³⁺phosphors synthesized by high temperature solid phase method,the synthetic Na₃In F₆ in the monoclinic system P2?/c space group crystallization.Under the excitation of 450 nm blue light,the emission peak of Cr³⁺in Na₃In F₆ phosphor was 763 nm,and the half-maximum was 103 nm.At this time,the emission peak of Yb³⁺covered the near-infrared light region of 930-1050 nm,and the half-maximum increased to 183 nm.By adjusting the doping concentration of Cr³⁺and Yb³⁺,revealed that the emission intensity of Yb³⁺increased as the Cr³⁺doping concentration rised,indicating the existence of energy transfer.The incorporation of Yb³⁺expanded the emission bandwidth of phosphor,which facilitated the achievement of stronger near-infrared emission.Thermal stability tests conducted on phosphors found that the luminescence intensity of Cr³⁺remained 19%of that of room temperature at 150℃,while that of Yb³⁺remained 43%of that of room temperature.（3）Na₂Mg Sc F₇ doped with rare earth ions was prepared for the first time by combining hydrothermal and high temperature solid-phase reaction.X-ray powder diffraction（XRD）combined with Rietveld refinement confirm the Na₂Mg Sc F₇crystallize in Imma group,and the lattice parameters a=10.40860?,b=7.32804?,c=7.52879?,α=β=γ=90°,V=574.256?³.Through doping the Tb³⁺or Eu³⁺ions,downshifting emissions of yellow-green or red can be obtained in NMSF,respectively.Upconversion emissions can also be designed with the doping Yb³⁺-Er³⁺,Yb³⁺-Tm³⁺,Yb³⁺-Ho³⁺,and Er³⁺.Moreover,the Na₂Mg Sc F₇:Er³⁺exhibited green upconversion emission under the excitation of 980 nm,while exhibited red emission under the excitation of 1532 nm.Finally,recognizable patterns were obtained under the excitation of 254,365,and 980 nm,indicating that the as-prepared phosphors can be applied to multicolor anti-counterfeiting.It was worth mentioning that the synthesis method of this system opens up a new way for the synthesis of novel fluorides.