| As a new type of solid-state light source, light-emitting diodes (LEDs) haveattracted considerable attention due to their excellent advantages, such as energysaving, small volume, long operational lifetime and environmental friendliness.It is widely used in all kinds of instructions, displays, adornment, back light andurban night scene, etc. There are there approaches to achieve white LED.Among this methods, the white LEDs contructed via blue LED chip with yellowphosphors have been commercial. Because of their high luminescent efficiency.Ce3+-activated yttrium aluminum garnet is a well known yellow phosphor andhas been widely used for white LED based on blue LED chips. It has thecharacteristics of wide light-emitting spectral range, high luminescent efficiency,and excellent physical and chemical stability. It can absorb blue light given outby blue LED chip and emit yellow green light at the same time.Yellow greenlight and the rest blue light are complementary and they together synthesis whitelight. YAG: Ce luminescence spectrum has the problem of lacking of red lightcomponents, which results in lower white LED color rendering index. Inprevious research work, we found that add PbO in YAG: Ce3+can make the red emission peak of Ce3+shift. This article introduce that dope the Pb2+ion (PbO)into YAG: Ce3+, L (Pr3+/Cr3+) system, which increase the overlap of the L ionexcitation spectrum and the emission spectrum of Ce3+in order to promoteenergy transfer efficiency between Ce3+and L3+, which makes the YAG: Ce3+, L(Pr3+/Cr3+) phosphor powder red component enhanced.This paper in order to compensate red light component. We used the hightemperature solid-state reaction method which mixes different kinds of therare-earth ions (Ce3+/Pr3+) red light with YAG: Ce3+phosphor to synthesis YAG:Ce3+, Pr3+phosphor. Then we can study different concentrations of Pb2+on YAG:Ce, L(L=Pr3+/Cr3+) phase, luminescence properties and the influence of thefluorescence lifetime of phosphor by doping Pb2+in the YAG: Ce, L(L=Pr3+/Cr3+)phosphor. The main results of the research are as follows:(1) It was found that the emission band of Ce3+in YAG: Ce3+, Pr3+phosphorsshifted to long wavelength region with the addition of Pb2+ions. Moreover, thered emission from Pr3+ions was enhanced. It may be attributed to the fact thatthe addition of Pb2+ions can affect the crystal field environment and make thecenter of gravity of5d energy level of Ce3+lower, so that the spectra overlapbetween the emission spectra of Ce3+ions and the excitation spectrum of Pr3+ions, which can improve the energy transfer efficiency from Ce3+to Pr3+. Whenthe concentration of PbO (x) is0.04mol, the shift of emission spectra of Ce3+and red/yellow ratio all reached to the maximal value.(2) Change the ion species glow red light, replace the Cr3+with the Pr3+, doping Pb2+in YAG: Ce3+, Cr3+phosphor can increase the energy transfer efficiencybetween Ce3+-Cr3+. Red/yellow light ratio reached the maximal value when theconcentration of PbO is0.0075mol, it also can improve the color renderingindex.(3) Change the solvent type to study the influence of different cosolvent on YAG:Ce3+, Pr3+Pb2+ions towards the phase of phosphor and emission spectrum.Theresult shows that: adding cosolvent hardly change the position of the diffractionpeak, and no new emission spectrum diffraction peaks appear; when addingcosolvent with a mixture of BaF2and HBO3each at3wt percent, the emissionspectrum reached the highest intensity. It is much higher than individuallyadding cosolvent HBO3and BaF2emission. It is about257.7%emissionintensity comparing with the intensity when adding BaF2sample only, and195.7%emission intensity when adding HBO3sample only.(4) Change the heating rate, and study the influence of different high heatingrate on the YAG: Ce3+, Cr3+phosphor. The results show that: with the increasingof the heating rate, the samples intensity increased firstly and then decreased.The samples emission intensity reached the maximal value when the heatingrate is6oC/min. |
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