Synthesis And Spectral Properties Of Rare Earth Ions Doped Fluoride Phosphors

As a good matrix material to manufacture the rare earth ions doped phosphors,the rare earth fluoride endows with unique light,electricity and magnetism properties due to the abundant 4f energy level of rare earth elements,low phonon energy and good chemical stability.Thus,the rare earth ions doped fluoride material has aroused rapidly growing interest from more and more researchers.In this paper,we successfully synthesized several kinds of rare earth ions doped fluoride luminescent materials via the hydrothermal and water bath methods.The synthesis conditions,formation mechanism,the luminescent properties and energy transfer mechanism of some rare earth ions were studied systematically.The main contents of the research work is as follows:1.The monodisperse and uniform?-NaYF₄:Ln³⁺(Ln=Eu³⁺,Tb³⁺,Tm³⁺,Sm³⁺,Ho³⁺)microtubes were successfully synthesized via a simple hydrothermal method employing Y?OH?CO₃ colloid spheres as precursors.The possible formation mechanism was studied on the basis of a series of time-dependent control experiments and its intrinsic crystal structure.In?-NaYF₄:0.07 Tb³⁺,yEu³⁺series phosphors,the luminescence color of phosphors gradually changes from light green to yellow and orange,and finally reaches red with the increase of Eu³⁺concentration.The energy transfer?ET?mechanism from Tb³⁺to Eu³⁺was demonstrated to be a dipole-dipole interaction by I-H model.2.Different morphologies of?-NaLuF₄ crystals?hexagonal prisms and square nanosheets?were successfully fabricated via a two-step hydrothermal method under different pH values condition.The Tb³⁺ion is as the probe ion to research the effects of sizes and morphologies on the emission intensities of the samples,and the?-NaLuF₄ hexagonal prism?pH=9.0?is best for the luminescence.In?-NaLuF₄:0.03Tm³⁺,yDy³⁺series phosphors,this emission can be tuned from blue to sapphire to pale green with appropriately modulating the Tm³⁺/Dy³⁺doping concentration.The experimental and theoretical results show that the ET mechanism from Tm³⁺to Dy³⁺is a dipole-dipole interaction.3.The Na₅Gd₉F₃₂:Ln³⁺sub-microspheres were successfully synthesized via a simple water bath method employing colloidal Gd?OH?CO₃ spheres as templates.The luminescence properties of Na₅Gd₉F₃₂:Ln³⁺?Ln=Eu,Tb,Dy,Sm,Ho?phosphors were investigated in detail.In Na₅Gd₉F₃₂:0.03Tb³⁺,yEu³⁺series phosphors,by appropriately adjusting the Tb³⁺/Eu³⁺dopant concentrations ratio or using different excitation wavelengths,the tunable photoluminescence can be obtained and tuned from light green via yellow and orange to red.In addition,the ET routes were researched in the Tb³⁺/Eu³⁺co-doped Na₅Gd₉F₃₂ sample,and there are two ET routes?Gd?Tb?Eu and Gd?Eu?.Moreover,the ET mechanism between Tb³⁺and Eu³⁺was demonstrated to be a dipole-dipole interaction by I-H model.4.The Na₅Lu₉F₃₂:Ln³⁺?Ln=Eu,Tb,Dy,Sm?nanoparticle was synthesized via a two-step hydrothermal method.In Na₅Lu₉F₃₂:xTb³⁺series phosphors,the optimum doping concentration of Tb³⁺is 7mol%,whose fluorescence quantum efficiency is11.68%.In addition,the thermal stability of Na₅Lu₉F₃₂:0.05 Tb³⁺sample was investigated,and the emission intensity still remained 79.3%at 493 K compared with that at 293 K,indicating that it has good thermal stability and color stability.Through Arrhenius formula,the activation energy??E?was calculated as 0.14 eV.