The Synthesis And Luminescence Of Rare Earth Niobates, Tatanlates, Phosphates Micro And Nano-sized Phosphors

Orthoniobates,orthotantalates and orthophosphates have been shown to be the hosts for rare earth ions to emit different luminescence due to their safety and stable properties.In this paper,using rare earth complexes aromatic carboxylic acid(ortho hydroxylbenzoic acid)as the rare earth species and composing with organic polymers Polyethylene(PEG)as dispersing medium template and urea as a fuel,the hybrid precursor have been formed by in-situ co-precipitation method.Then after the calcination of the hybrid precursors,several series of rare earth niobates and tantalates phosphors have been synthesized,which present regulation morphologies just like cobblestone,grain and column,such as RENbO₄:RE³⁺(RE=Eu,Tb,Dy,Er,Sm), (Y,Gd)NbO₄:Eu³⁺/Tb³⁺,LnNbO₄:Bi³⁺,LnNbO₄:x mol%Bi³⁺,5 mol%Dy³⁺,GdTaO₄: Ln³⁺(Ln=Eu³⁺,Tb³⁺,Dy³⁺,Er³⁺,Sm³⁺,Pr³⁺),(Y,Gd)TaO₄:Eu³⁺,Zn₃Nb₂O₈:Er³⁺, Eu³⁺,Dy³⁺,LnVTa₂O₉:5 mol%Eu³⁺/Dy³⁺,YNb_xV_1-xO₄:Eu³⁺,Dy³⁺,Er³⁺,Sm³⁺, RE(Nb,V)O₄:x mol%Dy³⁺,RE(Nb,V)O₄:5 mol%Dy³⁺,x mol%Bi³⁺;RE(Nb,P)O₄: RE³⁺(Re=Eu,Tb,Dy,Er,Sin):YNb_xTa_1-xO₄:Eu³⁺,Dy³⁺.Under UV excitation,they emit different luminescence.At the same time,blue Sr₂CeO₄ and Eu³⁺/Dy³⁺-doped Sr₂CeO₄ phosphors have been fabricated from the hybrid precursors and their luminescence properties have been investigated.Furthermore,LaPO₄:Eu³⁺/Tb³⁺nanowires,nanorods and nanoparticles have been synthesized by adjusting the hydrothermal solvent.Using anhydrous Ethanol as solvent, the as-formed LaPO₄ powders show pure hexagonal phase and nanowires-like morphology,just like the product prepared using distilled water as solvent.However, with the presence of DMF,the morphology and structure of LaPO₄ have been changed. With the volume ratio of DMF to distilled water increase,the structure has been changed from hexagonal phase to monoclinic phase and the morphology from nanowires to nanoparticles.Obviously without any template or the higher temperature or alkaline conditions,the control on the morphology and structure of LaPO₄:Eu³⁺/ Tb³⁺is possible through adjusting the volume ratio of DMF to distilled water. Additionally,using DMF(N,N-dimethylformamide)as solvents,the final product show different results,which depend on the nature of lanthanide ion.As for the light lanthanide ions from La³⁺to Nd³⁺,the white powders of lanthanide ions coprecipitated with PO₄^3-have been obtained.While for the medium lanthanide ions from Eu³⁺to Dy³⁺,the final products depend on the volume of the DMF solvents.When volume of DMF is large,the final products show white powders and while volume of DMF is small,the inorganic-organic gels have been formed.However,for heavy lanthanide ions,the inorganic-organic gels always have been obtained in spite of the volume of DMF.In all the emission spectra of Eu³⁺- doped rare earth orthophosphates phosphors, ⁵D₀-⁷F₁ orange emission line are predominant,indicating that more Eu³⁺ion occupies a site with an inversion center.Besides this,through altering the hydrothermal temperature,Eu³⁺-doped YPO₄,LaPO₄ and GdPO₄ phosphors have been obtained, which present different morphologies and structures by comparing to the product under identical temperature.Especially,tetrahedral phase YPO₄:Eu³⁺exhibits interesting column-like morphology.Finally,Zn₃(PO₄)₂:Eu³⁺nano-sized phosphors have been prepared by the hydrothermal and the emission lines of Eu³⁺have been examined,among which,the intensity of ⁵D₀-⁷F₁ orange emission is the strongest.By changing the hydrothermal temperature and pH Value,the morphology and structure of the final products have been investigated.As a result,when the pH Value is from 4 to 8,the orthorhombic phase of hydrated Zn₃(PO₄)₂:Eu³⁺have been obtained,which show nanorods and nanoparticles,respectively.However,the morphology and structure of hydrated Zn₃(PO₄)₂:Eu³⁺show little difference with the increasing of the hydrothermal temperature.