【作者】 仲华；

【导师】 陈宝玖； 李香萍；

【作者基本信息】 大连海事大学 ， 凝聚态物理， 2012， 硕士

【摘要】 白光发光二极管(WLED)是一种寿命长、节能、环保、工作电压低和响应速度快的新型固态照明光源,被誉为第四代照明光源,近年来备受科研人员的广泛关注。实现WLED主要有两大途径,一种是将红、绿、蓝三基色LED芯片组装实现白光发射,另一种是将蓝/紫光LED芯片与稀土荧光粉相结合产生白光发射。荧光粉制备技术的进步对WLED的发展起着重要的推动作用,本论文针对紫外光芯片激发的钛酸盐荧光材料展开研究。三价稀土离子具有丰富的能级,其掺杂的发光材料在绿色照明、生物荧光标识、短波长激光器、信息显示以及光电子学等领域有着广阔的应用前景。钛酸盐具有良好的热稳定性和化学稳定性,是一种很好的发光基质材料。本论文采用传统的高温固相法,成功制备了稀土钛酸盐体系发光材料,运用X射线衍射、荧光光谱等测试分析手段,对样品的物相组成、发光性能以及热稳定性等进行了分析。主要内容和结果如下：采用高温固相法,制备了Eu3+掺杂NaGdTiO4红光发射荧光粉。对合成NaGdTiO4:Eu3+的工艺条件进行了实验研究,确定了最佳的原料配比。荧光光谱测试结果表明,样品可被紫外光有效激发,基质到激活离子存在有效的能量传递,且样品具有质量较好的红光发射和良好的热稳定性。通过对不同温度下样品荧光光谱和衰减曲线的测试分析,得出能量传递是Eu3+发生荧光热猝灭的主要机理。采用高温固相法,制备了Dy3+掺杂NaGdTiO4白光发射荧光粉。研究了反应原料、助熔剂含量、激活剂浓度对荧光粉发光性质的影响。测试结果表明,激活离子的掺杂浓度不影响样品的晶体结构,样品具有质量较好的白光发射,且随着温度的上升,样品发光出现热猝灭现象。通过对不同温度下样品荧光衰减曲线与发射强度的分析,确定cross-over效应是引起Dy3+发生荧光热猝灭的主要原因。采用高温固相法,成功制备了Er3+/Yb3+共掺杂NaGdTiO4上转换荧光粉。确定在NaGdTiO4:Er3+/Yb3+荧光粉中Er3+的绿光发射和红光发射均为两光子过程,分析了Er3+掺杂浓度对上转换发光的影响,最后对上转换发光的具体过程进行了讨论。更多还原

【Abstract】 As a solid state lighting source, white light emitting diodes (WLEDs), which are known as the forth-generation lighting source, have many advantages such as long serving longevity, energy saving, environmental amity, requirement of low voltage support and fast response, etc. and have received extensive attention. Generally, there are two major routes to achieve WLED:one is by assembling red, green and blue LED chips to achieve white light emission; another is by combining blue or ultraviolet LED chip with rare earth doped phosphors to achieve white light emission. The progress in preparation technology of phosphors greatly drives the development of WLED. In this dissertation, the rare earth ions doped titanate materials for UV chip-based WLEDs were investigated.Trivalent rare earth ions (RE3+) possess many levels, and RE3+ doped luminescent materials have broad application prospects in the lighting, biological fluorescence labling, short wavelength lasers, information displays and optoelectronics. Titanates have good thermal and chemical stability and are excellent matrics for RE3+ luminescence centers. In this dissertation, rare earth doped titanate luminescent materials were successfully synthesized through traditional high temperature solid-state method. The synthesis conditions, luminescence properties and thermal stability of the titanate phosphors were analyzed by means of x-ray diffraction (XRD), fluorescence spectroscopy, and chromatric calculations. The main contents and results are as follows.The Eu3+ doped NaGdTiO4 red phosphors were synthesized through high temperature solid-state method. The optimal preparation condition of NaGdTiO4:Eu3+ phosphors was studied, and that the optimized ratio of raw materials was determined. The results showed that there is a strong energy transfer from the matrix to the Eu3+ ions; the samples can be effectively excited by UV light and have intense red light emission. The analysis of fluorescence decay curves at different temperatures confirmed that energy transfer from Eu3+ to quenching center is the major mechanism of fluorescence thermal quenching of Eu3+ ions in NaGdTiO4 phosphors.The Dy3+ doped NaGdTiO4 white light phosphors were synthesized through high temperature solid-state method. The influences of the raw materials, flux content and the activator concentration on the properties of the phosphors were studied in detail. It was found that the doping concentration of Dy3+ ions does not affect the crystal structure of the samples and there is an effective energy transfer from the matrix to the Dy3+ ions; the high quality white light emission can be achieved from the studied phosphors. With the increase of temperature the thermal quenching phenomenon happened. Analysis on the temperature-dependent fluorescence decay curves and the emission intensity indicated that the cross-over process is the major mechanism of fluorescence thermal quenching of Dy3+ ions in NaGdTiO4 phosphors.The Er3+/Yb3+ co-doped NaGdTiO4 upconversion phosphors were synthesized through high temperature solid-state reaction method. It was found that the two-photon process is responsible for both green and red upconversion emissions of Er3+ in NaGdTiO4:Er3+/Yb3+ phosphors. The relationship between Er3+ doping concentration and upconversion luminescence intensity was studied. Finally, the specific process of upconversion luminescence of NaGdTiO4:Er3+/Yb3+ phosphor was discussed.更多还原