The Study Of Preparation And Luminescence Properties Of The Rare-earth-doped The Host Of Ba₃InB₉O₁₈and MgNb₂O₆

Rare-earth-doped solid-state luminescent materials have gradually become a hot spot material for studying photoluminescence with the rapid development of lighting and display fields.As a basic research,we are dedicated to researching new functional compounds,exploring their luminescence mechanism and unique luminescent phenomena.Due to the diversity of B-O groups,borate not only has presented a variety of structural types and adapted most of the metal cations,but also has mild and simple synthesis method and stable physical and chemical properties,making the borate-based has become one of the hot systems for studying rare earth luminescent materials.The niobate are widely used in various photoelectric materials due to their excellent physicochemical properties of piezoelectricity,ferroelectricity,electro-optics,electro-optic and photorefraction,etc.The MNb₂O₆（M stand for a divalent cation）chemical compounds of niobate has important research value in the field of luminescent materials because of its NbO⁶ octahedron can serve as a luminescence center.In order to find novel photoluminescent materials,we synthesized the co-doped Ba₃InB₉O₁₈:Eu³⁺/Tb³⁺,the single-doped and co-doped MgNb₂O₆:Dy³⁺/Tm³⁺phosphors by high temperature solid-state synthesis method at first time.And a series of studies of luminescence characteristics,luminescence mechanism and crystal structure of two-system phosphors had been conducted,such as X-ray diffraction（XRD）,Rietveld structure refinement,photoluminescence excitation（PLE）and emission（PL）under ultraviolet（UV）and vacuum ultraviolet（VUV）excited,high or low temperature variable temperature fluorescence spectroscopy,decay curve and chromaticity diagram（CIE）.After the pure phase was prepared,the structural refinement of the Ba₃InB₉O₁₈:Eu³⁺/Tb³⁺ co-doped sample was performed using the Rietveld method.It was proved that the Eu³⁺/Tb³⁺ doping did not change the original lattice structure and a series of unit cell parameters were obtained.The comparative experiment comparing rare earth ions in different occupancy was also attempted,and it was found that Eu³⁺/Tb³⁺ tends to occupy the In³⁺ position with a single position.It is well known that Eu3’ and Tb3’single-doped Ba₃InB₉O₁₈ samples exhibit strong red and green emission,respectively.In this paper,the relationship between Eu³⁺/Tb³⁺ doping concentration and luminescence intensity was reported,and the excitation and emission fluorescence spectra of the sample aiming at different luminescence centers was recorded under ultraviolet and vacuum ultraviolet,respectively.The low temperature variable temperature fluorescence spectrum also was tested.There exists energy transfer from Tb³⁺ to Eu³⁺ owing to the analysis of doping concentration and luminescence intensity and the fluorescence lifetime test results of Eu³⁺ and Tb³⁺ in the same group of samples.The process of luminescence of the co-doped sample was discussed by the energy level diagram.In addition,the emission color of Ba₃InB₉O₁₈:Eu³⁺/Tb³⁺ co-doped phosphors can be properly adjusted in the green,yellow,and red regions by adjusting the concentration of doped ions and the excitation wavelength,indicating that the samples have great value for research of tunable color function as well as flat panel display and lighting.In the study of MgNb₂O₆:Dy³⁺/Tm³⁺ systems,the fluorescence spectrum of host of MgNb₂O₆,Dy³⁺/Tm³⁺ single and double-doped samples under UV and VUV were compared.Among them,due to the charge transfer between the Nb atoms in the center of the NbO6 octahedral group and the O ligand,the MgNb₂O₆ matrix emits cyan light with a broad band of 350-600 nm and emits more intensely at low temperatures.The Dy³⁺/Tm³⁺,single-doped samples emit yellow and blue light,and the corresponding doping quenching concentrations are 4.5%mol and 3%mol,respectively.When we added Tm³⁺ to the phosphors with Dy³⁺ concentration of 4.5%mol,the emission color could be shifted from yellowish to warm yellow and warm white.The MgNb₂O₆-based samples exhibited thermal quenching at high temperatures,but the chromaticity coordinates moved to the white light region.According to the analysis of spectral overlap and the decrease of the average decay time of the characteristic emission of the activator as the concentration of the doping ions increases,the phenomenon of energy transfer between the matrix and the activator is demonstrated.In view of the stability of physicochemical properties,proper excitation and emission wavelength range and sufficient luminescence intensity,the host-sensitized phosphors of MgNb₂O₆:Dy³⁺/Tm³⁺ have crucial significance for the study of solid-state lighting applications.