The Synthesis And Photoluminescence Properties Of Single-Phased Phosphate And Silicate Phosphors For White LEDs

As the fourth generation lighting source,white-light-emitting has advantages of low energy consumption,high luminous intensity,long life and environmental protection.Nowadays,the main scheme of W-LED is to combine the LED chip and the phosphor to produce white light,which is the fluorescent conversion W-LED.The current main program is that YAG:Ce3+ yellow phosphor and InGaN blue LED chip combination to produce white light.Due to the lack of red component,a new solution that the UV LED chip and the three color phosphor combine to white light can be presented.The white light obtained by this method has high luminous intensity and excellent color rendering index.However,the luminous efficiency is low because of the reabsorption of blue phosphor.Therefore,a scheme for the generation of white light by the combination of UV LED chip and single matrix phosphor is proposed.This system has excellent stability and reproducibility.The color and the performance of the light depend entirely on the combination of phosphor in the study of the fluorescent conversion type,hence the focus of W-LED is to research good phosphor.In this paper,a series of Ca3Y(PO4)3 phosphors and KBaYSi2O7 phosphors doped with different rare earth ions were synthesized by high temperature solid-state method.The phase,luminescent properties and energy transfer between the ions were characterized.The main results obtained are listed as follow:(1)Ca3Y(PO4)3:Eu2+,Sm3+ phosphors were synthesized by high temperature solid-state method in a reducing atmosphere.The samples were characterized by XRD spectra,diffuse reflectance spectra,excitation emission spectra,color coordinate and fluorescence decay spectra.The XRD spectra of the samples were compared with the JCPDS standard cards,and no obvious changes were observed.The results showed that the incorporation of a small amount of Eu2+ ions and Sm3+ ions did not change the lattice structure of the matrix.Under 405 nm excitation,Eu2+ and Sm3+ ions were co-activated so as to produce white light.Meanwhile,the emitting color can be tuned from blue-green to white and eventually to orange-red by precisely controlling the ratio of Eu2+ to Sm3+.According to the empirical formula,CCT value was calculated as 5058 K indicated that the phosphor that can be used for indoor lighting.The energy transfer between Eu2+ ions and Sm3+ ions was testified by the fluorescence decay curve,the mechanism of energy transfer was also analyzed.The results indicate that as-prepared Ca3Y(PO4)3:Eu2+,Sm3+phosphor has a good application prospect in NUV pumped W-LED.(2)Ca3Y(PO4)3:Dy3+ phosphors were synthesized by high temperature solid-state method.The samples were characterized by XRD spectra,diffuse reflectance spectra,excitation emission spectra and color coordinate.The XRD profiles were found to be a good agreement with that reported in JCPDS card No.44-0319,indicating that the incorporation of Dy3+ ions did not affect the crystal structure.Under 365 nm excitation,the emission peaks at 485 nm,578 nm and 664 nm are in due to transition from 4M21/2 to 6H13/2,4F9/2 to 6H13/2 and 4G11/2 to 6H11/2 levels,respectively.The optimal concentration of Dy3+ ions is 5 mol%.It is very close to the standard white point when 5 mol%Dy3+ ions doped with the matrix,and the CCT value is 5482 K.It is proved that the phosphor has a good application prospect in white lighting.The energy transfer mechanism from Dy3+ to Dy3+ is demonstrated to be a dipole-dipole interaction based on the concentration quenching.In conclusion,Ca3Y(PO4)3:Dy3+ phosphor has great significance in NUV pumped white-light-emitting diodes phosphor.(3)KBaYSi2O7:Ce3+ phosphors were synthesized by high temperature solid-state method in CO reduction atmosphere.The XRD spectra show that the diffraction peaks of the samples are consistent with the diffraction peaks of the standard cards.It is proved that the incorporation of a small account of Ce3+ions did not change the crystal structure of the matrix.Under 354 nm excitation,the emission spectrum of KBaYSi2O7:Ce3+ phosphor exhibits a broad peak at 448 nm based on from 5d to 4f energy transition.The optimal concentration of Ce3+ ions is 2 mol%.According to fitting result,the multipolar interaction for energy transfer between Ce3+ ions in mainly depend on dipole-dipole interaction.All in all,the results indicate that KBaYSi2O7:Ce3+ phosphors possess great potential for white LED applications.