Prepanation And Luminescent Properties Of Rare Earth-transition Metal Ions Doped Silicate Matrix Phosphors

Rare earth and transition metal doped luminescent materials are very important for us,which are mainly used in energy-saving lamps,semiconductor lighting,flat panel display,scintillation crystals and other fields.They have become one of the supporting materials in energy-saving lighting,information display,photoelectric detection and other fields,and play an increasingly important role in the progress of science and technology and social development.In this paper,silicates with very stable physical and chemical properties are used as matrix materials.A series of new inorganic luminescent materials are synthesized by single doping and co doping of europium ion and manganese ion respectively.The properties of these materials are systematically studied by means of XRD,SEM,excitation and emission spectra.The main research results are as follows:(1)Novel red-emitting Eu3+-doped Na2ZnSiO4(NZS)phosphors were synthesized by solid reaction at a high temperature.The crystal structure was confirmed by X-ray diffraction and the morphology was examined by scanning electron microscopy.The luminescence properties of NaZnSiO4:xEu3+(NZS:xEu)phosphors were studyed by photoluminescence excitation,emission spectra and decay curves.The phosphors exhibit abnormal intense red emission which located at 702nm due to the 5D0?7F4 transition of Eu3+under the excitation of 3 93nm and it makes the CIE chromaticity coordinates of the phosphors to fall in a red region.This phenomenon may be explained by the highly polarizable chemical circumstance.The optimum Eu3+doping concentration of NZS:xEu is determined to be x=0.08.The critical distance between Eu3+was calculated to be 13.36A.The quadrupole-quadrupole interaction of Eu3+ions may explain the concentration quenching mechanism.The decay curves show double exponential behavior for all concentrations of Eu3+ions and the lifetimes varied from 0.67 to 1.3ms when the Eu3+doping concentration increased in the range of 4-12mol%The quantum yield of Na2ZnSiO4:0.08Eu3+phosphor is calculated to be as high as 88.76%.The present work suggests that Na2ZnSiO4:Eu3+phosphor is a promising candidate as a red component for NUV LEDs application.(2)Novel rare-earth free green-emitting phosphor Na2ZnSiO4:Mn2+ was prepared by solid reaction in the carbon reducing atmosphere at 900?.The crystal structure was confirmed by X-ray diffraction and the structure information was refined by the Rietveld method.The luminescence properties of Na2ZnSiO4:Mn2+phosphors as a function of Mn2+concentrations were investigated.The excitation band peaking at?359,383,427,449,and 467nm are attributed to ground level 6A1(6S)to excited levels 4E(4D),4T2(4D),[4A(4G),4E(4G)],4T2(4G),and 4T1(4G)transitions of Mn2+ion,respectively,which indicates that Na2ZnSiO4:Mn2+phosphor may be excited by(near)ultraviolet and blue region light-emitting diode chip.The narrow emission band peaks at-515nm generated by 4T1(4G)?6A1(6S)transition of the Mn2+ can exhibit strong green emission.The luminescence mechanism was explained by the Tanabe-Sugano diagram.The optimum Mn2+doping concentration was 0.5mol%.The critical distance between Mn2+was calculated to be 33.72A.The dipole-dipole interaction of Mn2+ ions may explain the concentration quenching mechanism.With the Mn2+ doping concentration increasing in the range of 0.2-0.8mol%,the lifetime of this phosphor decreased from 7.506 to 7.391ms.These phosphors also possessed good thermal stability at high temperature,and the emission intensity at 125? was about 74.9%of that at 25?.The present work suggests that Na2ZnSiO4:Mn2+ phosphor is a kind of potential green-emitting phosphor to provide a bright green component in the red/green/blue tri-color system w-LEDs.(3)Eu2+and Mn2+co-doped CaMgSi2O6 phosphors were prepared via solid reaction at a high temperature.Their crystal structures,luminescence properties and energy transfer between Eu2+and Mn2+were investigated systematically.Under excitation at 350 nm,CaMgSi2O6:Eu2+,Mn2+phosphors showed a wide excitation band ranging from 240 to 420 nm and two broad emission bands that peaked at 445 nm and 675 nm,which were ascribed to the 4f-5d transition of Eu2+ and the 4T1?6A1 transition of Mn2+ions,respectively.The critical distance has been calculated by the concentration quenching method and the energy transfer mechanism from the Eu2+ to Mn2+ ions is demonstrated to be the dipole-dipole interaction.The color coordinate can be tuned from blue(0.204,0.093)to purplish red(0.265,0.123)by properly varying the ratio of Eu2+/Mn2+.