【作者】 袁双龙；

【导师】 陈国荣；

【作者基本信息】 华东理工大学 ， 材料科学与工程， 2011， 博士

【摘要】 由于高发光效率、节约能源、长寿命、环境友好、小体积及不含汞,白光发光二极管近十年来吸引了研究者们极大的注意。主要有两种方法制造白光发光二极管。目前最常用的方法是复合近紫外或者蓝光发光二极管芯片与光转换荧光粉。本论文首先详细总结了这些光转换荧光粉。由于这些荧光粉具有如差的化学稳定性、低效率或者较高的合成条件,因此需要研究新的荧光粉体系或者制备方法。本文中,通过高温固相法在不同的合成条件制备了Eu2+和Mn2+共掺杂的Ba2Mg(B03)2、Eu2+掺杂的氧磷灰石结构氧硅酸盐Mx-yLn10-xSi6027-x/2 (M= Mg, Ca, Sr, Ba, Ln=Y, La, Gd)及其氧氮化物、Eu2+掺杂的Sr2Si5N8,详细研究了它们的光致发光性质。本文通过XRD分析了Eu2+和Mn2+共掺杂的Ba2Mg(B03)2的相结构。此荧光粉在365nm光激发下发射橙红光。通过光致发光光谱和发光衰减时间分析,详细研究了Mn2+对发光性质的影响。结果表明,Mn2+不作为发光中心存在,但是使得Eu2+的长波发射纯化,因此通过改变Mn2+浓度可以获得可调的橙黄至橙红发射。通过烧成条件研究,成功制备了Eu2+掺杂的氧磷灰石结构的化学式为Mx-yLnlo-xSi6027-x/2的氧硅酸盐荧光粉。研究了烧成温度对相结构和光致发光性质的影响,获得了优化的烧成温度。通过光致发光光谱详细研究了M2+及其含量、Ln3+和Eu2+浓度对发光性质的影响。这些荧光粉具有范围从280-450nm的宽的激发带,在365nm光激发下发射从蓝绿到橙光。讨论了Eu2+在不同晶格位置的发射,结果表明,短波和长波发射带分别归因于Eu2+在氧磷灰石晶格中的4f和6h位置。也讨论了Eu2+在两个晶格位置的能量传递效应。通过SEM研究了荧光粉颗粒的形貌和颗粒尺寸,结果显示,其具有结晶完整的超细粉体颗粒。引入N3-通常导致Eu2+发射峰红移,因此,在NH3气氛下制备了上述氧硅酸盐荧光粉。通过O/N含量分析、XRD和光致发光光谱,研究了Sr的原料对氮含量、相结构和发光性质的影响。结果表明,使用SrCN2:Eu比SrCO3作为Sr的原料所制备的荧光粉具有更高的发光强度。通过XRD谱,详细研究了SrCN2:Eu作为原料时烧成温度对荧光粉相结构的影响并讨论了固相反应过程。通过测试69-325K范围内温度对发光光谱的影响研究,讨论了Eu2+的发射机理。结果显示,可以观察到两个发射带,且随着温度增加长波发射峰蓝移但短波发射峰位置不变,两个发射峰均发生了浓度猝灭,讨论了可能的浓度猝灭机理。Sr2Si5N8：Eu2+是一种白光LED用性能优异的红色荧光粉,本文应用SrCN2:Eu作为原料在NH3气氛下通过较低的烧成温度合成了此氮化物荧光粉。通过XRD、O/N含量分析和发光光谱研究了合成的Sr2Si5N8：Eu2+荧光粉的晶相、氮含量和发光性质,与文献方法相比其发射峰蓝移,讨论了蓝移的原因。由于在制备前述氧氮化物和氮化物过程中SrCN2:Eu2+发挥了重要作用,因此通过高温固相反应在NH3气氛中制备了不同含量Eu2+掺杂的MCN2(M=Ca, Sr),通过XRD谱研究了它们的相结构。由于其潜在的光致发光能力,详细研究了其光学性质和在低温下的发光光谱。反射光谱测试结果表明SrCN2的禁带宽度为4.56eV,在77K温度下SrCN2:Eu2+发射峰波长为610nm的宽带光谱,其激发峰范围为350-520nm。随着测试温度增加,发射强度显著减小,表明SrCN2:Eu2+的猝灭温度低,探讨了温度猝灭机理。更多还原

【Abstract】 White light emitting diodes (WLEDs) have attracted many attentions of researcher in recent years due to high luminous efficiency, energy savings, long persistence, environmental friendliness, small volume and lack of toxic mercury. Two basic approaches can be used to fabricate white LEDs. The conventional approach is the combination of near ultraviolet or blue light LED chips with photo convert phosphors. In this thesis, the phosphors have been summarized in detail firstly. Because of some disadvantages of present phosphors, such as poor chemical stability, low efficiency or critical synthesis conditions, novel phosphors or preparation methods have to be developed.In this thesis, Eu2+ and Mn2+ codoped Ba2Mg(BO3)2, Eu2+ doped oxyapatite-like oxysilicates Mx-yLn10-xSi6027-x/2 (M= Mg, Ca, Sr, Ba, Ln= Y, La, Gd) and its oxynitrides, Eu2+ doped Sr2Si5Ng have been prepared by high temperature solid state at different synthesis conditions and their photoluminescence properties have been investigated in detail.In present work, the phase structure of Eu2+ and Mn2+ codoped Ba2Mg(BO3)2 phosphors were determined by XRD. The phosphors emit orangish-red light under 365 nm excitation. By photoluminescence spectra and decay time measurements, the effect of Mn2+ on photoluminescence properties has been investigated in detail. The results show that Mn2+ don’t act as activators but purify long wavelength emission of Eu2+ and thus the tunable orangish-yellow to orangish-red emission is obtained by varying Mn2+ concentration.Eu2+ doped oxyapatite-like oxysilicates phosphors with general chemical formula Mx-yLn10-xSi6O27-x/2:Eu2+ have been successfully synthesized by studying the firing conditions. The effect of firing temperature on phase structure and photoluminescence properties have been studied and then the optimized temperature was obtained. By the measurements of photoluminescence spectra, the effect of M2+ ions, Ln ions, M2+ ions concentrations and Eu2+ concentration on photoluminescence spectra have been investigated in detail. These phosphors show broad excitation bands ranging from 280-450 nm and exhibit from bluish-green to orange light under 365 nm excitation. The emissions of Eu2+ at different crystallographic sites have been discussed. The results show that short wavelength emission band attributes to the emission of Eu2+ at 4f site and long wavelength to that of Eu2+ at 6h site. The energy transfer between Eu2+ at two sites has been discussed. By SEM, the morphology and particle size has been determined and the results show that the phosphors have good crystallization with super fine size. Introduction of N3- generally leads to redshift emission of Eu2+, therefore, oxyapatite-like oxysilicates above mentioned have been prepared under NH3 atmosphere. The effect of Sr resources on nitrogen content, phase structure and photoluminescence properties have been studied by O/N analyzer, XRD and photoluminescence spectra. The results suggest that the phosphor using SrCN2:Eu as Sr resource exhibits higher emission intensity than that of using SrCO3. The Effect of firing temperature on phase structure of phosphors using SrCN2:Eu as starting materials have been investigated in detail and the solid state reaction process has been discussed by XRD measurements. For investigating the mechanism of Eu2+ emission, the effect of temperature at the range of 69-325K on photoluminescence spectra have been studied. The results indicate that two distinguished emission bands can be observed clearly and blueshift of long wavelength emission occurs with increasing temperature but short wavelength emission don’t change except for temperature quenching. The possible mechanism has been discussed.Sr2Si5N8:Eu2+ is a excellent red emission phosphor for WLEDs application. In present work, Sr2Si5N8:Eu2+ phosphor has been synthesized at low temperature by using SrCN2:Eu as starting materials under NH3 atmosphere. The phase, nitrogen content and photoluminescence properties of Sr2Si5N8:Eu2+ phosphor have been determined by XRD, O/N analyzer and photoluminescence spectra. Blueshift of emission band was observed and the mechanism has been discussed.Due to playing a key role in preparing oxynitrides and nitrides above mentioned, Eu2+ doped MCN2 (Ca,Sr) with different Eu2+ contents were prepared by high temperature solid state reaction under NH3 atmosphere. The phase structures have been determined by XRD spectra. Because of potential photoluminescence ability, the optical properties and photoluminescence spectra at low temperature of SrCN2:Eu have been investigated in detail. The results show that SrCN2 has an energy gap of 4.56 eV by the reflection spectra and Eu2+ doped SrCN2 shows a broad band emission with a peak at 610 nm when it is excited by 350-520 nm at 77 K. With the temperature increasing, the emission intensity decreases remarkably, indicating that Eu2+ doped SrCN2 has a low quenching temperature. The temperature quenching mechanism has been investigated.更多还原