Sr₂CeO₄及其掺杂纳米发光材料的制备与发光性能研究

【作者】 贺香红；

【导师】 余锡宾；

【作者基本信息】 上海师范大学 ， 物理化学， 2004， 硕士

【摘要】 本文从Sr₂CeO₄的合成方法、发光性能、发光机理、掺杂Sr₂CeO₄荧光体等方面，综述了Sr₂CeO₄及掺杂Sr₂CeO₄荧光体的研究进展。首次采用柠檬酸-凝胶法，通过优化制备工艺条件，成功地合成了Sr₂CeO₄及金属离子掺杂的Sr₂CeO₄纳米荧光粉，并且应用X射线衍射、拉曼光谱、红外光谱、热重分析、紫外-可见吸收光谱、荧光光谱、透射电镜、原子力显微镜等先进测试方法进行了表征，得到了以下主要结论： 在合成Sr₂CeO₄纳米荧光体时，根据材料的晶体结构和发光性能，柠檬酸-凝胶法优于高温固相法。采用柠檬酸-凝胶法成功地制得Sr₂CeO₄纳米荧光材料，粉体材料呈白色，所含杂相极少，颗粒呈球形，平均粒径大约40-50nm，粒径分布较窄，使用前不需要球磨。该材料在紫外光激发下，发出很强的蓝白色荧光，发射主峰位于470nm附近，可用于蓝白光显示等领域。 制备工艺条件对Sr₂CeO₄纳米荧光粉的发光性能有较大的影响，其中煅烧温度的影响最明显；当煅烧温度为1000℃，柠檬酸与金属离子的比是3:1，起始溶液的pH值为7时，发光强度达最大。 本文还详细研究了铕离子掺杂的Sr₂CeO₄纳米荧光体的发光性能、浓度猝灭、能量传递以及共掺杂离子对Sr₂CeO₄:Eu³⁺发光性能的影响。所制得的Sr₂CeO₄:Eu³⁺荧光粉体为白色，粒径微细。当掺杂量较大时，在紫外光照射下，发出较强的红色荧光。Sr₂CeO₄:Eu³⁺荧光体的激发光谱由两部分组成：一个宽的激发带和属于Eu³⁺离子f-f跃迁的锐线谱（峰位分别位于：395、466、532nm），发射光谱中除了出现常见的发射峰如：585nm（⁵D₀→⁷F₁）、616nm（⁵D₀→⁷F₂）、655nm（⁵D₀→⁷F₃）和704nm（⁵D₀→⁷F₄）外，还包含有来自较高能级激发态⁵D₁的跃迁发射，即：509nm（⁵D₁→⁷F₀）、534nm（⁵D₁→⁷F₁）、554nm（⁵D₁→⁷F₂）。初步表明Eu³⁺离子在Sr₂CeO₄基质中处于偏离或无反演中心的格位上。 Sr₂CeO₄基质中Eu³⁺的猝灭浓度高达22mol％，这可能是由于：（1）在Sr₂CeO₄晶格中，Eu³⁺离子之间的交叉驰豫作用即：⁵D₁+⁷F₀→⁵D₀+⁷F₁较弱；（2）采用柠檬酸-凝胶法制得的荧光体中铕离子的分布更均匀，为有效激发和发射提供了条件；（3）Sr₂CeO₄基质特殊的一维链式结构最大限度了减少了激发能在传递过程中上海师范大学硕士学位论文的损失。而浓度碎灭的机理可能是交换作用。 在srZceo;:Eu3+荧光体中，存在着从基质到激活剂离子的能量传递，该能量传递可能是通过链内或链与链之间的交换作用进行的。共掺杂离子如稀土离子La3+、ed3+、Y3+和碱金属离子Li+、Na+、K+等能增强sfZeeo;:Eu3+荧光体的发光性能，这主要是由于共掺杂后形成了能量传递网的结果，共掺入的稀土离子可能还起着补偿电荷的作用。 上述结果预示着所合成的SrZCeO;纳米荧光粉体有较好的理论与应用研究价值，是一种极具发展前途的基质材料和发光材料。本论文为SrZCeo;纳米荧光粉体材料的理论与应用研究开发提供了参考依据。可以预测，本文所合成的srZceo4:E矿十川+（Rn+为共掺杂金属离子）纳米荧光体，经过系列合成工艺优化、二次应用特性探索和改进，将具有广阔的应用前景，可用于蓝白光或红光显示等领域。更多还原

【Abstract】 In this paper, from the preparation method to photoluminescence properties and luminescence mechanism, the research progress of pure and doped Sr2CeO4 phosphors were reviewed. To our best knowledge, for the first time, pure and doped Sr2CeO4 nano-sized phosphors, was successfully synthesized through citrate-gel method, after optimizing preparation conditions. This paper also investigated the structures, spectral characters, luminescence behaviors, particles size and morphology of pure and doped Sr2CeO4 phosphors by X-ray diffraction (XRD), FT infrared, Raman spectrum, thermogravimetric analysis (TG), ultraviolet and visible absorption spectrum, photoluminescence spectrum, transmissions electron microscopy (TEM) and atomic force microscopy (ATM), respectively. The conclusions are as follows:As for preparation of Sr2CeO4 phosphor, based on the crystal structure and luminescent property, the citrate-gel method is better than solid-state method at high temperature, because this phosphor can be synthesized at lower sintering temperature through citrate-gel route. This as-prepared Sr2CeO4 phosphor with white body-color, contains little impurities phase and the Sr2CeO4 phase is dominant. The Sr2CeO4 phosphor particles are sphere and have particles size 40-50nm and narrow size distribution. There is no need for it to be milled before application in lamps or other luminescence display field. Under excitation with irradiation of UV rays, these nano-phosphors exhibit strong blue-white luminescence, which peaks at about 470 nm. Therefore, it has good potential for application as a blue-white phosphor.Luminescence properties of Sr2CeO4 nano-phosphors can be affected by preparation conditions, in which the sintering temperature is dominant. When the sintering temperature, the ratio of citric acid to metal ions and the pH value of precursor solution is 1000癈, 3 : 1 and 7, respectively, it owns maximum emission intensity of photoluminescence.In the present paper, the luminescence properties, concentration quenching, energy transfer and effect of co-doping ions on the luminescence of Sr2CeO4:Eu3+ phosphor are also studied in details. The as-prepared Sr2CeO4:Eu3+ nano-sizedsamples, with white body-color and smaller mean particle size, exhibit a strong red emission under UV excitation. The excitation spectra shows a broad intense band and a number of small peaks centered at wavelengths extending from 380 nm to 540 nm corresponding to the inner 4f-shell excitations of Eu3+ (the strongest one is at 466 nm for 7F0-5L6). From the measured fluorescence spectra of Sr2CeO4:Eu3+ nano-phosphors, apart from transitions emission of 5Do excited state 5Do -?F|(585 nm),5D0 @7F2(616 nm),5D0 @7F3(655 nm),5D0@7F4 (704 nm), the following transitions emission from 5D1 excited state of Eu3+ 5D1@7F0 (509 nm),5D1@7F1 (534 nm),5D1@7F2 (554 nm) have been observed. It is revealed that the quenching concentration for the 5Do-7F2 emission of Eu3+ in this host is as high as 22 mol%. This may be due to the facts that the probability of cross relaxation is lower and energy loss is very little in the course of energy transfer between two chains or inter-chain. In addition, energy transfer from host Sr2CeO4 to activator Eu3+ was observed inSr2CeO4: Eu3+ phosphor. The host-to-activator energy migration mechanism may be carried out by exchanging between two chains or inter-chain in Sr2CeO4 host lattice. The relative fluorescence intensities of rare earth ion (La3+-,Gd3+-, and Y3+- ) or alkaline ion( Li+-, Na+-, K+-) co-doped Sr2CeO4: Eu3+ phosphors were higher than that of Eu3+-doped Sr2CeO4.This emission enhancement mainly resulted from the fact that formation of energy transfer network after rare earth ion (La3+-,Gd3+-, and Y3+- ) or alkaline ion ( Li+-, Na+-, K+-) co-doping into Sr2CeO4 : Eu3+ phosphor.All the results revealed that the as-prepared Sr2CeO4 nano-sized phosphor has better theoretical and application potential. It is an excellent host and luminescent material, which owns splendid development prospects. It is predicted that a更多还原