【作者】 吕伟；

【导师】 张家骅；

【作者基本信息】 中国科学院研究生院（长春光学精密机械与物理研究所） ， 凝聚态物理， 2012， 博士

【摘要】 白光发光二极管（LED）由于其具有体积小、发热量低、耗电量小、寿命长、反应速度快等优点，被誉为第四代照明光源，应用前景十分广阔。而其中利用荧光粉转换实现白光LED是现今研究的主流。目前主要采用以下两种方法：第一种方法即用蓝光LED结合发黄光的荧光粉，或者用蓝光LED配合发绿色光和发红色光的荧光粉，合成白光；第二种方法采用紫外或近紫外LED去激发红、绿、蓝三种荧光粉产生白光。两种方法各有优势，第一种方法效率较高，适合普通照明。第二种方法组合的白光LED则可实现高显色性和好的彩稳定性，在高质量和特种照明领域具有重要应用。目前，适合蓝光LED发绿色光荧光粉及适合紫外管芯发出红绿蓝的单一基质荧光粉十分缺乏。因此为获得高效率与高质量白光，迫切需要研制新型荧光粉。本论文选择Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺,Mn²⁺及BaMg₂Al₆Si₉O₃₀:Eu²⁺, Tb³⁺, Mn²⁺荧光粉材料体系，系统地研究Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺,Mn²⁺材料在蓝光及BaMg₂Al₆Si₉O₃₀:Eu²⁺, Tb³⁺, Mn²⁺材料在近紫外光激发下的发光特性、能量传递过程及机理，具体的研究内容及结果如下：1.利用高温固相法于还原气氛下制备了Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺荧光粉。Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺荧光粉的合成是通过在（2-x）CaO-xZnO-SiO₂-CaCl₂（0≤x≤1.1）体系中逐渐变化x得到。实验表明，随着Zn的含量增加，样品的相逐渐由Ca₃SiO₄Cl₂转变为Ca₈Zn（SiO₄）₄Cl₂，期间伴随着样品在450nm处的激发位置逐渐增强。在蓝光激发下，对Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺与目前热点荧光粉发光强度进行了比较。可以看出，Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺的发光积分强度是目前热点绿色荧光粉Ca₈Mg（SiO₄）₄Cl₂:Eu²⁺的1.3倍，并与Ca₃Sc₂Si₃O₁₂:Ce³⁺相近。利用测得的漫反射与荧光寿命数据，分析了Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺发光增强的原因，证实了加Zn增强的原因主要是吸收增强引起的。将所得绿色Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺荧光粉与蓝光管芯进行封装，制成了色纯度好的绿光LED。表明Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺荧光粉作为绿色荧光材料非常适合应用于蓝光基LED。2.研究了Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺,Mn²⁺中Eu²⁺向Mn²⁺能量传递的动力学过程。在Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺,Mn²⁺中，观察到了来自Mn²⁺的⁴T1－⁶A1的黄光发射，实现了Eu²⁺向Mn²⁺的高效敏化发光。利用测得的荧光寿命数据。分别计算了理论和实验与Mn²⁺掺杂浓度相关的Eu^2-向Mn²⁺能量传递的速率、效率及发射强度比等微观参量。理论与实验符合的非常好。3.利用高温固相法制备了一种全彩色白光BaMg₂Al₆Si₉O₃₀:Eu²⁺, Tb³⁺, Mn²⁺荧光粉。通过对荧光光谱，能量传递效率，以及寿命的研究，证实了Eu²⁺-Mn²⁺和Eu^2--Tb³⁺之间的能量传递。在BaMg₂Al₆Si₉O₃₀:Eu²⁺体系中，发射光谱由两个谱带组成，分别位于370，450nm处。其中，370nm的发射带为Eu²⁺（I）占据Ba2+离子处于弱场的发射，而450nm的发射带为Eu²⁺（Ⅱ）占据Mg₂+离子处于强场的发射。分析表明Tb³⁺的能量主要来源于Eu²⁺（Ⅱ），而Mn²⁺的能量是由Eu²⁺（I）和Eu²⁺（Ⅱ）共同贡献的。在365nm近紫外光激发下，观察到材料具有白光发射，白光是由450nm，540nm，和610nm的三个谱带组成，分别来源于Eu²⁺, Tb³⁺, Mn²⁺的发射。通过控制Tb³⁺/Mn^2-的相对含量，可以得到色坐标为（0.31，0.30），显色指数为90，色温为5374K的单一白光。实验表明，该单一白光荧光粉在新一代白光照明领域具有广阔的应用前景。4.通过在BaMg₂Al₆Si₉O₃₀:Eu²⁺, Mn²⁺中利用Sr取代Ba,获得了SrMg₂Al₆Si₉O₃₀:Eu^2-, Mn²⁺。研究了Sr取代Ba中光谱的变化过程。深入探讨了SrMg₂Al₆Si₉O₃₀:Eu²⁺, Mn²⁺中Eu²⁺向Mn²⁺能量传递的动力学过程。比较了BaMg₂Al₆Si₉O₃₀:Eu²⁺, Mn²⁺与SrMg₂Al₆Si₉O₃₀:Eu²⁺, Mn^2-的温度特性，其间的差异主要是由不同的激活能造成的。更多还原

【Abstract】 The light-emitting diodes （LEDs）-based white light sources have receivedincreasing interest in recent years for their promising applications on illuminationswith advantages in power efficiency, reliability, long lifetime, and environmentalprotection. Generally, there are two ways to gain white light: one is combination of ablue LED （460nm） with a yellow phosphor or green and red phosphor. The secondapproach to achieve white light is combination of a near-UV（NUV） or UV LED withred, green, and blue phosphor. The blue LED can achieve high luminous efficiency,while the near-ultraviolet （UV） based white LEDs can show high color renderingindex and stability, and have more extensive application on the filed of specialillumination. At present, there are very few inorganic green phosphors for blue LEDand a single-phase full-color emitting phosphor with environmental stability andnontoxicity for NUV LEDs. In this paper, Ca8Zn（SiO4）4Cl2:Eu2+,Mn2+andBaMg2Al6Si9O30:Eu2+, Tb3+, Mn2+are chosed and their luminescent properties, energytransfer and mechanism have been studied. The main results obtained are listed asfollows:1. Eu2+activated Ca8Zn（SiO4）4Cl2were prepared by high temperature solid statereaction with nominal composition of （2-x）CaO-xZnO-SiO2-CaCl2（0≤x≤1.1）. It is observed that the material phase gradually converts from Ca₃SiO₄Cl₂:Eu²⁺toCa₈Zn（SiO₄）₄Cl₂:Eu²⁺followed by improved luminescent properties withincreasing x. The two phosphors both emit with a maximum at505nm.Significantly, Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺shows a more intense excitation band in theblue centered at450nm. Upon450nm excitation, the integrated emissionintensity of Ca₈Zn （SiO₄）₄Cl₂:Eu²⁺is1.3times that of Ca₈Mg（SiO₄）₄Cl₂:Eu²⁺andnearly the same as that of Ca₃Sc₂Si₃O₁₂: Ce³⁺phosphors. Attempts to understandthe origins of the intense luminescence are presented on the basis of diffusereflection spectra and fluorescence decays of Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺in comparisonwith related phosphors. The present results suggest that Ca₈Zn（SiO₄）₄Cl₂:Eu²⁺could be a promising green emitting phosphor for excitation by blue light emittingdiodes.2. Luminescence and energy transfer in Eu²⁺and Mn²⁺codoped Ca₈Zn（SiO₄）₄Cl₂are investigated. The emission spectra of the phosphors show a green band at505nm of Eu²⁺and a yellow band at550nm of Mn²⁺. The ratio of the yellowemission550nm the green505nm obtained from emission spectra is consistentwith the theoretical calculation based on energy transfer and lifetimemeasurements.3. A series of single-phase full-color emitting BaMg₂Al₆Si₉O₃₀:Eu²⁺, Tb³⁺, Mn²⁺phosphors have been synthesized by solid state reaction. Energy transfer fromEu²⁺to Tb³⁺and Eu²⁺to Mn²⁺in BaMg₂Al₆Si₉O₃₀host matrix is studied byluminescence spectra, energy transfer efficiency and lifetimes. InBaMg₂Al₆Si₉O₃₀:Eu²⁺, the PL spectrum consists of two bands, located at about376nm and450nm, respectively. Results indicate that the band at376nm isassigned to Eu²⁺（I） occupying Ba2+with weak crystal field, and the other one at450nm corresponds to Eu²⁺（Ⅱ） occupying Mg₂+with strong crystal field. Theenergy transfer leads to the following results:（1） the energy transfer of Eu²⁺-Tb³⁺is dominated by Eu²⁺（Ⅱ）–Tb³⁺transfer rather than Eu²⁺（I）–Tb³⁺transfer.（2） theenergy of the red emission of Mn²⁺is considered to come from both Eu²⁺（I） andEu²⁺（Ⅱ）.（3） the ratio of the red emission of Mn²⁺to the emission of Eu²⁺byexperiment is consistent with the theoretical calculation basing on energy transferand lifetime measurements. The wavelength-tunable white light can be realized bycoupling the emission bands centered at450nm,542nm and610nm ascribed tothe contribution from Eu²⁺and Tb³⁺and Mn²⁺, respectively. By properly tuning the relative composition of Tb³⁺/Mn²⁺, chromaticity coordinates of （0.31,0.30）,high color rendering index Ra=90and correlated color temperature CCT=5374Kcan be achieved upon excitation of UV light. We have demonstrated that thevaried emitted color from blue to green or red and eventually to white can beachieved by properly tuning the relative ratio of Tb³⁺and Mn²⁺. All these resultsindicate that BaMg₂Al₆Si₉O₃₀:Eu²⁺, Tb³⁺, Mn²⁺is a promising single-compositionphosphor for application involving white light LED.4. Eu²⁺and Eu²⁺-Mn²⁺codoped （Ba, Sr） Mg₂Al₆Si₉O₃₀phosphors have beensynthesized by solid state reaction, and their luminescent properties areinvestigated. A detail analysis on the energy transfer from Eu²⁺to Mn²⁺inSrMg₂Al₆Si₉O₃₀host is presented, which indicates the energy of the red emissionof Mn²⁺is derived mainly from Eu²⁺（I）. We have also demonstrated thatBaMg₂Al₆Si₉O₃₀: Eu²⁺, Mn²⁺exhibits better thermal quenching properties thanthat of SrMg₂Al₆Si₉O₃₀: Eu²⁺, Mn²⁺because of bigger activation energy.更多还原