| White LED possess the advantages of energy saving and environmental friendly,high luminous efficiency,long lifetime,small in size,rapid response speed,which make it becomes the fourth generation of lighting system to displace the traditional incandescent and fluorescent lamps.As an important part of white LED,the phosphor plays a crucial role in the performance of LED.Therefore,the development of new types of phosphors for WLED is of great significance to academics and practical applicationNitride phosphors have been attracted much attention in recent years because of their excellent physical and chemical stability and high luminous efficiency.In this dissertation,novel nitride luminescent materials for NUV or blue chips pumped white LED were designed and synthesized via high temperature solid state reaction.X-ray Diffraction(XRD),Transmission Electron Microscopy(TEM),photoluminescence excitation and emission were used to characterize the structure and optical properties of the phosphors,and the relationship between structure and optical properties was clarified.The main contents are described as follow1.A series of Ce3+and Mn2+co-doped,white light emitting Mg2Y3Si3O11N phosphors were synthesized via high temperature solid state reaction.The apatite structure of this phosphor was confirmed by XRD and TEM.The atomic site occupation of Mg2+and Y3+in the phosphor was illustrated by Rietveld refinement and emission spectra.Mg2-yY3-xSi3O11N:xCe3+,yMn2+exhibited a strong absorption in the range of 250-380 nm,which meant it could match the NUV chip well.Under the excitation of 340 nm,two main peaks could be observed in the emission spectrum peaking at 440 nm and 610 nm,which originated from Ce3+ and Mn2+,respectively.The emission spectrum showed broad emission band in 390 nm to 750 nm,covering most of visible light region,which meant white light emitting in a single host can be realized.Warm white light emission could be further achieved by adjusting the concentrations of Ce3+and Mn2+The mechanism of energy transfer had been discussed and was demonstrated to be a resonant type via a dipole-quadrupole interaction.The temperature dependence emissions,quantum efficiency and correlated color temperature(CCT)of samples were measured and the samples exhibit excellent properties.All the results indicate that this phosphor is a potential candidate for NUV chip pumped white LED applications2.A series of MgY2-xAl3Si2O11N:xCe3+phosphors were synthesized via high temperature solid state reactions.The garnet structure was confirmed by XRD and structural refinement was carried out via the GSAS program to evaluate the accuracy of structural parameters.The results showed N3-was incorporated into the host lattice.The excitation spectrum shows intense absorption in blue light region,indicating this phosphor could be pumped by blue LED chip.Under the excitation of 460nm,the phosphor emitted yellow-orange light peaking at 563nm for phosphor with the optimum concentration of Ce3+(6%).Compared with YAG:Ce3+,the emission spectra of MgY2-xAl3Si2O11N:xCe3+phosphors shifted to red side,which can be attributed to the larger covalency,crystal field splitting energy and Stokes shift.Combine the phosphor with a blue chip,it could be found that the color rendering index(79.1)was higher and color temperature(6933K)was lower in comparison with the LED employs the YAG:Ce3+ Phosphor.In conclusion,this phosphor is a promising candidate for blue chip pumped white LED. |
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