Synthesis And Properties Of Rare Earth Fluoride Oxides And Vanadates Luminescent Materials With Diverse Morphologies

In recent years,micro/nano rare earth luminescent materials have been widely used in fields like phosphors,photocatalysis,flat panel displays,bioluminescent probes.In addition to the inherent physical properties of activator ions,the choice of the desired host matrix is critical to the luminescent properties.Rare earth oxyfluoride has attracted much attention due to its stable chemical and thermal properties and low photonic energy.Vanadate is an excellent matrix sensitizing material.The properties of micro/nano matrix materials are closely related to their morphology,size and other factors,so the controllability of micro/nano matrix materials with specific morphology is of great significance.In this paper,rare earth oxyfluoride and vanadate luminescent materials were synthesized by hydrothermal synthesis method,and the phase,structure,morphology,influencing factors and spectra of the materials were studied.The main work is as follows:（1）Rhombohedral phase YOF and quadrature phase Y₆O₅F₈ microdisks of uniform size and good dispersibility were synthesized by hydrothermal and calcination without adding a template or any surfactant.The effects of different molar ratios of NH₄HCO₃ and NaF on the product were studied.The YOF,Y₆O₅F₈,NaYF₄ and YF₃ products with different morphologies were obtained.The up-conversion and down-conversion luminescence properties of YOF and Y₆O₅F₈ microdisks were studied by doping Eu³⁺,Yb³⁺,Er³⁺and Yb³⁺,Tm³⁺,respectively.The reasons for the different excitation and emission spectra of the two crystals were explained from the perspective of the difference in unit cell structure.The peaks in spectra were sharp and strong.The linear fluorescence emission indicates that the YOF and Y6O5F8 microdisks can be used as excellent fluorescent matrix materials.（2）Square-shaped YOF crystallites with uniform particle size and good dispersibility were synthesized by hydrothermal and calcination methods.The reaction temperature plays an crucial role in controlling the morphology of the products.When the temperature is higher than 160°C and 120°C,the product can not maintain the shape of the tetragonal sheet and produce a long tubular morphology.When the temperature is below 80 ^oC,it is not conducive to the smooth progress of the reaction.The YOF:Eu³⁺sample exhibits a strong fluorescence emission under ultraviolet excitation.Under 980 nm laser excitation,YOF:Yb³⁺,Er³⁺and YOF:Yb³⁺,Tm³⁺can exhibit their characteristic luminescence,and the peak shape is sharp,which proves that the tetragonal sheet-like YOF is an excellent fluorescent matrix material.（3）Octahedral YVO₄ microcrystalline material with good dispersion was prepared by one-step hydrothermal method by using polyacrylic acid（PAA）as a surfactant.During the synthesis process,the pH value of the initial solution has a great effect on the final morphology and crystallinity of the samples.When the pH is low,the product is a spheroidal structure.When the pH is 12.7,the obtained product is an octahedral structure,and the product with octahedral structure has the best crystallinity.The fluorescence spectra show that the octahedral YVO₄:Eu³⁺and YVO₄:Sm³⁺samples exhibit strong sensitization effect of VO₄³￣,and the samples can exhibit characteristic and excellent luminescence performance.