Preparation And Luminescent Properties Of Rare Earth Ion Doped NaYF₄ And NaY（MoO₄）₂ Phosphors

NaYF₄ and NaY（MoO₄）₂ matrices as important inorganic materials,because they have good thermal and chemical stability as well as excellent optical properties.Therefore,it has a wide range of applications in photoluminescence,photocatalysis and other frontier areas.At present,there are many researches on upconversion luminescence under 980nm light excitation.However,few researches on upconversion luminescence under near800nm light excitation.The excitation light of this band is beneficial to expand the application range of fluorescent materials.In this paper,rare earth doped NaYF₄ and NaY（MoO₄）₂upconversion luminescence materials were synthesized by hydrothermal method.The luminescence performance and upconversion luminescence mechanism of the materials were studied under ultraviolet and near infrared light excitation.X-ray diffraction（XRD）,scanning electron microscope（SEM）,fluorescence spectrum（FL）,CIE chromaticity coordinate and infrared spectrometer（FT-IR）were used to characterize the structure,morphology and luminescence performance of the synthesized samples.The effects of doping amount of rare earth ions,the p H value of the reaction solution,molar ratio of EDTA-2Na:Re³⁺and Y³⁺:F^-,annealing temperature on luminescence performance and matrix crystal morphology were analyzed.The upconversion luminescence properties of the same rare earth ion doped NaYF₄and NaY（MoO₄）₂matrices,the mechanism of rare earth ion upconversion luminescence and the influence of rare earth ion doping on the matrices crystal morphology were discussed.（1）The upconversion luminescent materials of NaYF₄:Eu³⁺were synthesized by hydrothermal method.The results show that the best doping amount of Eu³⁺is 14%under the excitation of 793nm.The concentration quenching will be produced when the doping amount is increased.The most optimal the p H value of the reaction solution is 6.The molar ratio of EDTA-2NA:Eu³⁺is 3:1.The molar ratio of Y³⁺:F^-is 1:7.The upconversion luminescence performance of NaYF₄:Eu³⁺is the best when upconversion luminescent materials of NaYF₄:Eu³⁺were synthesized under optimal conditions.β-NaYF₄of hexagonal phase were synthesized under optimal conditions with good luminescence.（2）The phosphors of NaY（MoO₄）₂:Er³⁺、NaY_（97%-x%）（MoO₄）₂:Dy³⁺_（x%）,Er³⁺_（3%）（x=1.0～5.0）and NaY_（98%-x%）（MoO₄）₂:Dy³⁺_（2%）,Er³⁺_（x%）（x=1.0～10.0）were synthesized by hydrothermal method.The results show that the luminescence intensity of NaY（MoO₄）₂:Er³⁺is the strongest when the doping amount of Er³⁺is 3%,the annealing temperature of 800℃and the p H value of the reaction solution is 3.For the luminescence properties of NaY（MoO₄）₂:Dy³⁺,Er³⁺,there is an energy transfer process of Dy³⁺→Er³⁺.The emission spectra of Er³⁺at 525nm,553nm and Dy³⁺at 479nm,574nm are also shown.The diffraction peak of the NaY（MoO₄）₂:Er³⁺corresponds to the NaY（MoO₄）₂standard card and belongs to the quadrate crystal system,indicating that the synthetic sample is the pure phase of NaY（MoO₄）₂.With the increase of annealing temperature,the diffraction peak are gradually strengthened and the peak shape are gradually sharp,indicating that the crystal formed tends to be perfect,among which the crystal type of the sample at 800℃is the most complete.（3）The upconversion luminescent phosphors of NaYF₄:Eu³⁺,NaY（MoO₄）₂:Eu³⁺,NaYF₄:Sm³⁺and NaY（MoO₄）₂:Sm³⁺were synthesized by hydrothermal method.The results show that doping of Eu³⁺and Sm³⁺have no effect on matrices crystal morphology.The upconversion emission peak position of rare earth ions are approximately same but the relative intensity are different in different matrices.Compared with NaYF₄as the matrix,the asymmetry of Eu³⁺and Sm³⁺occupancy position is higher when NaY（MoO₄）₂as the matrix,which leads to different luminescent intensity at different characteristic peak positions and different luminescent chromaticity:orange-red light and red light were emitted by preparative phosphors under excitation near 800nm.The samples with NaY（MoO₄）₂as the matrix emit purer red light.In particular,NaY（MoO₄）₂:Eu³⁺can produce high purity red light.