【作者】 杨雪峰；

【导师】 宁桂玲；

【作者基本信息】 大连理工大学 ， 化学工艺， 2009， 博士

【摘要】 以SrAl₂O₄：Eu²⁺，Dy³⁺为代表的铝酸盐长余辉材料，激发光谱范围广，发射光谱在可见光区，发光亮度高，余辉时间长，化学稳定性好，无毒无放射性，是一种环境友好材料。因此在安全应急、交通运输、建筑装潢、仪器仪表、电力、矿山、服装和工艺品等诸多领域有广泛应用。目前，研究制备新工艺提高发光粉的发光强度和余辉性能，完善长余辉发光机理，增加发光颜色品种以扩大发光材料应用范围是这一领域的研究热点。本论文对超细高亮度发光粉制备、铁杂质的猝灭效应、纳米氧化铕的制备及在长余辉材料中的应用、铝酸锂红色荧光粉的制备等多个方面进行系统的研究。本课题研究的结果对于粉体制备工艺的改进与创新、制备成本的降低、产品配方设计以及材料发光性能的改善等具有十分重要的意义。1．本文采用以聚环氧乙烷为模板的水热合成方法制备了无需研磨的高亮度SrAl₂O₄：Eu²⁺，Dy³⁺长余辉发光粉。借助于TG-DTG、XRD、TEM、SEM和荧光分光光度计等表征手段，对产物的形成过程、结构、形貌以及光谱性能进行了分析。结果表明，模板水热法能够制备尺寸均匀的介孔前驱物，有利于烧结反应充分进行，有利于降低烧结温度，得到的发光粉颗粒在几个微米左右，余辉起始发光强度高。模板水热法制备的发光粉样品Eu²⁺的临界猝灭浓度大约在10％左右，这一数值比采用高温固相法合成发光粉的临界猝灭浓度6．6％高得多。本章还系统地探讨了发光粉各个组分与发光性能之间的关系：通过改变SrO与Al₂O₃的比率，考察基质相组成与发光性能变化的关系，寻找相组成变化引起的材料发光强度的变化规律；通过研究助熔剂H₃BO₃与材料发光性能的关系，来考察H₃BO₃的最佳添加量：研究了Eu²⁺和Dy³⁺在SrAl₂O₄：Eu²⁺，Dy³⁺长余辉材料发光中的作用，结果表明Eu²⁺离子是发光中心，是引起材料发光的决定因素，Dy³⁺离子对Eu²⁺离子发光中心有辅助增强作用。2．但是，模板水热法工艺相对复杂，因此本文还开发了溶胶-凝胶纳米包覆法制备SrAl₂O₄：Eu²⁺，Dy³⁺长余辉发光粉，该制备方法工艺简单，适合大规模工艺生产。文中通过TEM研究了纳米包覆过程，结果表明纳米纤维状或絮状水合氧化铝均匀的包覆在碳酸锶表面，形成具有微小核壳结构的前驱物。TG和XRD分析结果证明烧结核壳结构的前驱物能够降低反应温度和提高产物晶相纯度，当烧结温度升到1000℃生成了单一的单斜晶系的SrAl₂O₄晶相，这一温度比固相法低300℃左右。SEM结果表明纳米包覆法制备的样品颗粒松散，平均尺寸在3μm左右。与高温固相法相比，纳米包覆法制备的材料发光强度和余辉时间都显著提高，这大大提高了长余辉产品的应用范围。SrAl₂O₄：Eu²⁺，Dy³⁺发光粉中点缺陷的形成及其在发光材料中的作用研究表明，缺陷Eu_Sr^x中的Eu²⁺既是发光中心也是余辉中心；Dy_Sr^·带有正电荷，具有捕获电子的能力，因而可作为电子陷阱：V_Sr^"带有负电荷，能捕获空穴，可作为空穴陷阱。3．考察了铁杂质对SrAl₂O₄：Eu²⁺，Dy³⁺长余辉材料发光性能的影响。结果表明，铁杂质对长余辉发光粉具有发光猝灭效应，铁浓度越高，长余辉发光越弱，这可以解释为铁杂质竞争能量抑制了Eu²⁺发光中心吸收能量，降低了电子和空穴的复合机率。实验数据验证了上述解释，同时证实了Fe³⁺离子是引起长余辉发光猝灭的主要因素。针对这个结果，本章提出了在前驱物制备过程中掺加Pr³⁺或者Bi³⁺离子，可以有效的抑制了Fe³⁺离子的猝灭影响。4．利用无模板水热方法制备了Eu（OH）₃和Eu₂O₃纳米棒，并将Eu₂O₃纳米棒应用到SrAl₂O₄：Eu²⁺，Dy³⁺发光粉制备中。结果表明纳米棒Eu（OH）₃为六方晶系，纳米棒Eu₂O₃为立方晶系，二者的直径分别为57nm和76nm。实验证明使用纳米氧化铕制备SrAl₂O₄：Eu²⁺，Dy³⁺发光粉，有利于Eu²⁺离子进入基质晶格，增加发光中心浓度，从而提高材料长余辉发光。5．采用溶胶-凝胶纳米包覆技术制备了新颖的γ-LiAlO₂：Eu³⁺红色荧光粉，对该材料的结构，形貌和发光性能进行系统的研究。研究结果表明产物结构为四方晶系，颗粒呈准球形，平均粒径约为1．5μm。该产品具有典型的Eu³⁺发射特征，发射主峰在612nm，发光颜色为红色。实验证明适宜的Eu³⁺离子浓度，烧结温度以及助熔剂H₃BO₃的加入量有助于增加材料的发光性能。更多还原

【Abstract】 SrAl₂O₄:Eu²⁺, Dy³⁺ system long afterglow materials have been accepted as one of the most important luminescent materials, due to the advantages of its wide excitation spectrum, visible emission range, high luminescent intensity, long duration, well chemical stability, no radiation, and environmental capability. These good luminescent properties result in an unexpectedly large field of applications, such as safety exigence, transportation, building and decorating, instruments and apparatuses, electricity, mines, clothing and arts. Currently, the researches focus on improving emission intensity and afterglow time, perfecting long afterglow luminescent mechanism and increasing the red luminescent production.In this paper, the synthesis of ultrafine and high intensity phosphors, quenching research of iron, preperation of Eu₂O₃ nano rod and its application in SrAl₂O₄:Eu²⁺, Dy³⁺ phosphor, and the synthesis of redγ-LiAlO₂:Eu³⁺ fluorescent were studied and investigated systematically. The results will bring on important significance at the side of improving preparation method, decreasing cost, perfecting recipe formulation and luminescent properties.1. SrAl₂O₄:Eu²⁺, Dy³⁺phosphors with high intensity and none milling were prepared by template-based hydrothermal method using nonionic polyethylene oxide as surfactants. The forming process, structure, morphology and luminescent properties of obtained products were characterized by means of TG-DTG, XRD, TEM, SEM and fluorescence spectrophotometer. The analysis results indicat that the precursor prepared by hydrothermal synthesis method are homogeneously mixed at the molecular level, leading to high reactivity of starting materials and the reduction of sintering temperature, the obtained phosphor powders are consist of uniform small grains and have better luminescence compared with that of solid state method. The critical quenching concentration of Eu²⁺ of the phosphors prepared by templating synthesis is about 10mol%, which is higher than that of solid state method of 6.6mol%.In this section, the relationship between composition of SrAl₂O₄:Eu²⁺, Dy³⁺ phosphor and its luminescence properities were researched. Through changing the ratio of SrO and Al₂O₃, the relation between the host phase and persistent luminescence was studied in order to search the changing regularity; the relation between B₃HO₃ and luminescence properities of product were also studied in order to confirm the optimal doped quantity; the roles of Eu²⁺ and Dy³⁺ in SrAl₂O₄:Eu²⁺, Dy³⁺phosphors were studies, and the results suggest that Eu²⁺ ions are luminescent center, which is the crucial factor, and Dy³⁺ ions play a role of assistant.2. Because of the cost problem of hydrothermal synthesis method, we explored sol-gel nano-coating method using to prepared SrAl₂O₄:Eu²⁺, Dy³⁺ phosphors. The method has the advantages of esay process, low cost and fitting for large production. In this section, the coasting process has been studied by TEM method, the results insicate that nanometer Al₂O₃ coat in the surface of SrCO₃ and become core-shell precursor. The TG and XRD results prove that reaction temperature is decreased and crystal purity is improved by shintering the core-shell precursor, pure monoclinic phase of SrAl_O4 has fomed when the sintering temperature reach to 1000℃, which is lower 300℃than solid state method. The SEM results indicate that the phosphors prepared by sol-gel nano-coating method have the average grain of 3μm. Compared with solid state method, sol-gel nano-coating method can improve the luminescence intensity and long afterglow time of SrAl₂O₄:Eu²⁺, Dy³⁺ phosphors, which expand the application.The research results for the roles of crystal defects in SrAl₂O₄:Eu²⁺, Dy³⁺ phosphors showed that Eu_Sr^x is not only luminescent center, but also afterglow center, Dy_Sr^·can be aselectron trap because of its positive charge which can capture electron, and V_Sr^" can be ashole trap because of its negative charge which can capture hole.3. The luminescence effect on SrAl₂O₄: Eu²⁺, Dy³⁺ phosphors arising from iron impurity was systemically studied in this paper. The results revealed that iron impurity cause quenching for persistent luminescence of SrAl₂O₄:Eu²⁺, Dy³⁺ phosphors, the higher the concentration of the iron is, the lower the persistent luminescence performance is. This can be explained that iron restricts the function of Eu²⁺ luminescent center and decreases the recombination probability between electrons and holes. The explaination was approved by further exploration, and it was observed that Fe³⁺ ions is the central factor which cause quenching for persistent luminescence. Aim at above result, it can be put forword that doping Pr³⁺ or Bi³⁺ ioins at the preparation of precursor can restrain the quchening effect of Fe³⁺ ions.4. Eu（OH）₃ and Eu₂O₃ nanorods were synthesized by a facile hydrothermal procedure without template, Eu₂O₃ nanorods was successfully applied for the preparation of SrAl₂O₄:Eu²⁺, Dy³⁺ phosphors. The results revealed that the obtained Eu（OH）₃ nanorods show hexagonal phase and Eu₂O₃ nanorods show cubic phase. The average size of Eu₂O₃ nanorods can be calculated of 90nm using Scherrer equation, which agrees with TEM results. Further exploration proved that Eu²⁺ ions can enter into SrAl₂O₄ host crystal lattice more easy when use Eu₂O₃ nanorods as the starting materials, which increase the concentrations of Eu²⁺ luminescent centre and improve the persistent luminescence of the SrAl₂O₄:Eu²⁺, Dy³⁺ phosphor. 5. A novel Eu³⁺-dopedγ-LiAlO₂ phosphor was successfully prepared by sol-gel nano-coating process. The structure, morphology and luminescence properties of the phosphor were detailed investigated. The results indicate that the obtained products show pure tetragonal phase and narrow size-distribution of about 1.5μm for the particles with sphere-like shape. Luminescence test indicated that theγ-LiAlO₂:Eu³⁺ phosphor emits an intense characteristic luminescence of Eu³⁺ ions with main peak 612nm, which show red colour. Further experiments proved that feasible concentration of Eu³⁺, sintering temperature and amount of H₃BO₃ can useful to improved the luminescence of the phosphor.更多还原