Synthesis And Luminescence Properties Of Rare Earth Ions Doped GdF₃ And Gd₄O₃F₆

Rare-earth fluorides have a broad spectral window and high band gap properties,allowing the electronic transition of doping ions to occur and avoid self-absorption.Its low phonon energy can effectively reduce the energy quenching of the excitation level.The characteristic of low phonon energy can effectively reduce the level of excitation energy quenching,excellent optical characteristics of these light-emitting time can be extended,and the quantum efficiency is improved.As an excellent substrate for rare earth doped luminescent materials,rare earth fluorides have been used in many fields such as light emitting devices,optical amplifiers,displays,and chemical sensors.Lanthanide oxyfluorides inherit the intrinsic merits of both fluoride and oxide counterparts featured by low-phonon energy and high thermal stability to ensure excellent luminescence performance of rare earth ion activators.The presence of oxygen may increase the excitation range to enhance the emission intensity through O^2-—Ln³⁺charge transfer.Therefore rare-earth-doped oxyfluoride is an ideal substrate for upconversion and downconversion luminescence.Meanwhile,since the high electronegativity,high chemical and thermal stability,oxyfluoride has been widely used in biosensing,nano-optical devices,phosphors,X-ray intensifying screen and the field of solar cell.The Gd³⁺in the gadolinium compounds can act as an intermediate medium,allowing energy to pass through the lattice of the gadolinium ions,accelerating the energy transfer process.Appropriate doping of a variety of lanthanide ions into the cerium matrix compound results in multicolor luminescence,and fluorescence emission from visible to invisible light can be obtained by co-doping or triple doping.In addition,the magnetic properties of gadolinium ions can be applied to biological research,such as contrast agents and bioseparation.Therefore,gadolinium ions are multifunctional materials that have both luminescent properties and magnetic properties.The research results in this paper are as following:1.GdF₃ with different morphologies and different crystal phases was obtained by using tartaric acid as precipitant and changing the experimental parameters such as solvent composition,pH value,tartaric acid dosage and reaction time.The GdF₃nanoparticles will show obvious changes with the different amounts of water and ethanol.Under the same conditions of solution composition and other conditions,orthorhombic phase and hexagonal phase of GdF₃ were prepared by changing the reaction time.Comparing different morphologies of GdF₃:Eu³⁺,the luminescence intensity of the mixed morphologies is the strongest.By comparing the luminescence intensities of different crystal phases,the hexagonal phase of GdF₃:Eu³⁺is more conducive to luminescence.2.We employ ionic liquid[OMIm]BF₄ to fabricate monodisperse Gd₄O₃F₆microcrystals.The precursor was synthesized by ionic liquid under hydrothermal conditions and then heated at 600 ^oC.The down-and up-conversion photoluminescence properties of Gd₄O₃F₆:Ln³⁺?Ln=Eu,Tb,Dy,Ho,Tm,Sm,Yb/Er,Yb/Ho?samples were investigated.A series of Dy³⁺/Eu³⁺co-doped Gd₄O₃F₆phosphor were also synthesized.In addition,the energy transfer mechanism between Dy³⁺and Eu³⁺ions were investigated in detail.Furthermore,the UC emission properties of the prepared Gd₄O₃F₆:Yb³⁺/Ln³⁺?Ln=Er,Ho?are investigated in detail.There is a two-photon process involved in the UC emission for Gd₄O₃F₆:10%Yb³⁺,1%Er³⁺sample.And upconversion mechanism of Gd₄O₃F₆:10%Yb³⁺,1%Ho³⁺via a three-photon process.