| Transition metal and rare earth ions doped phosphors are widely used in the field of lighting,display,decorative materials,biomedicine,etc..Silicate compounds are widely used as the matrix of luminescent materials because of their stable physical and chemical properties as well as excellent luminescent properties.In recent years,white LED have been widely used and promoted,in order to meet the demand of UV-near UV excitation conversion the white LED phosphors,silicate compounds Na2MgSiO4 was selected as matrix material,rare earth ions and transition metal ions were used as activators,prepared a series of phosphors samples by solid state method.The as-prepared phosphors can be excited effectively by near ultraviolet light(n-UV).This thesis systematically studied the crystal structure,doped ions occupation,photoluminescence property and energy transfer mechanism,etc..The main research achievements are as following:(1)A series of novel green phosphors Na2MgSiO4:xMn2+(x = 0-0.2)were synthesized by solid-state reaction at 950 ?.Analyzing its structure by GSAS Rietveld method,the structure refinement indicates that the as-prepared phosphors crystallize in orthorhombic phase with space group Pna21,and there are two Mg sites in host lattice.The doping ions Mn2+ are determined to occupy Mg sites,the tetrahedral position in the crystal,therefore,the peak of the emission spectrum was emitted by green light at 520nm.The emission spectra can be deconvoluted into two Gaussian components,corresponding to the two luminescence centers represented by Mn2+ ions occupying two different Mg positions.It is observed that the emission intensity of Mn2+ first increased and then decreased with the concentration of Mn2+ increasing,the optimum doping concentration was 8mol%.The concentration quenching mechanism was dipole-dipole interaction,and the critical distance was 13.42 A.The CIE chromaticity coordinate was(0.163,0.631)in green area.(2)A series of Na2(Mg1-xCax)SiO4:0.08Mn2+(x = 0-0.5)phosphors were synthesized by solid-state reaction.In addition,the effect of ions substitution on crystal structure and luminescent properties were investigated.Small amount of Ca2+ substitution for Mg2+didn't influenced crystal structure,but made the diffraction pattern has a slight blue shift.Appropriate amount of Ca2+ ions didn't affect the luminescence properties of Mn2+ but enhanced the emission intensity,the optimum doping concentration was x=0.4 and the intensity can be increased by 306%without changing the CIE obviously(0.169,0.720).This phosphors enriches the kinds of green phosphors which can be used in w-LED.(3)A series of Na2MgSiO4:Tb3+,xEu3+ phosphors were synthesized by solid-state reaction.The luminescent color of this phosphors can be achieved green-yellow-red continuous change by adjusting the ratio of Tb3+/Eu3+,the CIE chromaticity coordinate was(0.32,0.51)?(0.58,0.37).The emission spectrum monitored at 376 nm includes not only the Tb3+ characteristic emission profile but also the characteristic emission derived from Eu3+.The critical distance Rc between sensitizer and activator was 16.76 A,implying the energy transfer from Tb3+ to Eu3+ occurs via dipole-dipole mechanism,and the value of energy transfer efficiency reaches the maximum of 51.54%.These results indicate that the as-prepared Na2MgSiO4:Tb3+,Eu3+ phosphors have potential application in the field of w-LED. |
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