【作者】 钟伟；

【导师】 洪樟连；

【作者基本信息】 浙江大学 ， 材料科学与工程， 2008， 硕士

【摘要】 稀土发光材料是至今为止一类重要的光电功能材料,针对广泛使用的稀土三基色荧光粉材料存在的问题,采用核-壳结构的材料设计思想和制备技术,开展低成本高性能荧光粉材料的制备研究,对提高我国稀土资源的利用效率具有重要的意义。本文在总结稀土发光材料的原理与发展的基础上,提出采用核-壳结构的材料设计思想,利用Pechini溶胶-凝胶法,以单分散SiO₂微球作为核层材料合成了红色SiO₂@SrTiO₃:Pr,蓝色SiO₂@CaWO₄,以及绿色SiO₂@LaF₃:Ce,Tb三基色核-壳结构的荧光材料;采用XRD、FE-SEM、EDS、TEM、FT-IR、PL谱等手段,对荧光粉的颗粒形貌与尺寸大小、分散状态、包覆组分和物相种类及结构进行了测试与表征;对pr³⁺,Tb³⁺等稀土离子在核-壳结构发光材料中的发光性质,Ce³⁺与Tb³⁺之间的能量传递现象进行了重点分析,探讨和分析了材料制备工艺、包覆晶相种类与结构、核层与壳层结构状态、以及包覆荧光粉材料发光性能之间的关联规律。根据发光强度和材料热处理温度、包覆次数、前驱液中PEG浓度之间的关联规律,获得了适宜的包覆结构荧光粉制备的工艺条件范围。通过Pechini溶胶-凝胶法,合成了以SiO₂为核层材料的SiO₂@SrTiO₃:Pr核-壳结构荧光粉。结果表明,在目前工艺条件下能够在微球SiO₂表面包覆上SrTiO₃:Pr荧光粉,包覆荧光粉保持了单分散SiO₂微球的形貌特征;且壳层荧光粉厚度可以通过包覆次数进行调控。PL谱测试结果表明,包覆SiO₂@SrTiO₃:Pr荧光粉发出的是峰值位于615 nm的pr³⁺离子¹D₂→³H₄跃迁为主的红色光。通过Pechini溶胶-凝胶法,合成了以SiO₂为核层材料的SiO₂@CaWO₄核壳结构荧光粉。结果表明,在目前工艺条件下能够在微球SiO₂表面包覆上CaWO₄荧光粉,核一壳结构SiO₂@CaWO₄荧光粉表面光滑、没有显著团聚的球形颗粒,粒径大致在240 nm左右。PL谱测试表明,荧光粉的发光颜色为蓝色,分析认为这是由WO₄^2-作为独立发光中心发出的特征发光。通过Pechini溶胶-凝胶法,合成了以SiO₂为核层材料的SiO₂@LaF₃:Ce,Tb核-壳结构荧光粉。结果表明,包覆产物为球形、外表较光滑、粒径约在300nm左右的颗粒,不过颗粒间有较明显的团聚现象。XRD和EDS结果表明获得了SiO₂@LaF₃:Ce,Tb核-壳包覆结构的荧光粉。PL谱测试结果表明,在330 nm激发下,包覆产物SiO₂@LaF₃:Ce,Tb出现了四个中心位置分别在492 nm,544nm,586 nm和612 nm的主发射峰,它们分别属于Wb³⁺的⁵D₄→⁷F_J（J=6,5,4,3）跃迁发射。其中最强发射峰为544 nm,为绿光发射。研究表明,采用成本较低的SiO₂为核层材料,可以制备出球形的、尺寸可以根据核层颗粒大小进行调节的红色SiO₂@SrTiO₃:Pr,蓝色SiO₂@CaWO₄和绿色SiO₂@LaF₃:Ce,Tb三基色荧光粉材料。研究也发现,采用包覆结构制备的荧光粉发光强度与固相法相比较,还有一定的差距,需要从核层颗粒尺寸、制备工艺等方面继续研究。更多还原

【Abstract】 In nowdays,rare-earth luminescence material is still one of the most important optoelectronic functional materials.It is important to develop core@shell rare-earth phosphors with low cost and high performance so that to improve the utlization efficency of rare-earth resource in our nation.In this thesis,the principle and development of rare-earth phosphors were reviewed,and the design idea of core@shell structure was proposed to develop rare-earth phosphors including the SiO₂@SrTiO₃:Pr,blue SiO₂@CaWO₄ and green SiO₂@LaF₃:Ce,Tb trichromatic luminescent materials.Above mentioned core-shell structures phosphors were synthesized by Pechini sol-gel method using mono-dispersive SiO₂ microspheres as cores.The particle sizes,morphologies, component of shells and phases of as-prepared phosphors were investigated with XRD,FE-SEM,EDS,TEM,FT-IR,PL measurement,etc.The luminescent properties of rare reath ions(Pr³⁺,Tb³⁺)and energy transfer properties from Ce³⁺to Tb³⁺in core-shell structure luminescent materials were analyzed.The relationships among preparation techniques,composition and structure of shells,structures of shells and cores,and luminescent properties of these phosphors were discussed.The optimal synthetic conditions of core-shell phosphors were obtained according to the relations of luminescent intensities,heat-treatment temperature,coating times and the PEG concentrations in the precursor.Spherical SiO₂ particles were coated with SrTiO₃:Pr phospher as shell layer by Pechini sol-gel method.The FE-SEM and TEM results indicated that SrTiO₃:Pr can be coated on SiO₂ surfaces using this technique,and the core-shell structured phosphor particles are uniform and maintain the mono-dispersive morphology of initial SiO₂ core.The thickness of shell layer increased with increased coating cycles. The PL results showed that the core-shell phosphor emits red light originated from the ¹D₂→³H₄ transition of Pr³⁺ion with a maximum peak at 615 nm.Core-shell structured SiO₂@CaWO₄ phosphor was synthesized by coating mono-dispersive SiO₂ microspheres with CaWO₄ phosphor as shell layer by Pechini sol-gel method.The FE-SEM and TEM results showed that particles with core-shell structure have smooth surface,high dispersion state,spherical shape and narrow size distribution with an average size of about 300 nm.PL results showed that the phosphor emits a strong blue emission band that was suggested to be originated from the characterestic luminescence of WO₄^2-as independent luminescent centers.LaF3:Ce³⁺,Tb³⁺phosphor layer has been deposited successfully on mono-dispersed and spherical SiO₂ microspheres by Pechini sol-gel method.The FE-SEM results showed the core-shell structured phosphor maintains the morphology of SiO₂ with spherical shape and smooth surface with an average particle size of about 310 nm,nevertheless obvious aggregation occurs in this system.The XRD and EDS results indicated that SiO₂@LaF₃:Ce,Tb phosphors with core-shell structure were successfully synthesized.PL measurements indicated that under the excitation of 330 nm,four emission peaks occurred at 492 nm,544 nm,586 nm and 612 nm for SiO₂@LaF₃:Ce,Tb products,where these peaks were ascribed to the Tb³⁺⁵D₄→⁷F_J （J=6,5,4,3）transitions.The emission peak with greatest intensity is at 544 nm, which is characteristic of green light emission in the core-shell particles.Therefore,red emitted SiO₂@SrTiO₃:Pr,blue emitted SiO₂@CaWO₄ and green emitted SiO₂@LaF₃:Ce,Tb trichromatic luminescent phosphors with spherical shape, whose sizes could be tuned according to the size of core-shell particles,could be successfully synthesized using low-cost SiO₂ as core materials.It was also found that the photo-luminescent intensity of phosphors prepared by coating methods was not as good as that of phosphors prepared by solid state method,and it may be improved by controlling the core-shell particle sizes and synthetic techniques,etc.更多还原