稀土掺杂微纳复合材料的发光研究
文献类型：学位论文
| 作者 | 张德亮 |
| 学位类别 | 硕士 |
| 答辩日期 | 2011 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 张龙 |
| 关键词 | CaF2 氟磷玻璃 微纳复合 白光LED |
| 其他题名 | Luminescence of Rare Earth Doped Micro/Nano-Composites |
| 中文摘要 | 光转换效率高且能够大尺寸制备的发光材料无论是在超大功率激光还是照明显示领域都有迫切需求。传统的发光材料如玻璃由于其大尺寸制备简单，易于加工，掺杂均匀等优点成为各种稀土离子的掺杂基质而广泛应用于多种场合。然而其发光效率较低，耗能较大，在注重节能环保的今天限制了它的进一步发展与应用。而各种稀土掺杂的晶体材料则得益于其高效发光而在发光材料领域占据重要地位；但是大部分光谱性质优越的稀土掺杂激光晶体大尺寸制备困难，难以均匀掺杂，这成为制约它发展的最大缺陷。 利用复合材料理念，通过特殊工艺将微纳晶体均匀分散于玻璃中可以制备出玻璃-晶体微纳复合材料。这种材料结合了玻璃的大尺寸制备和晶体的高效发光，可以解决传统单组份发光材料易于制备而发光效率低或能高效发光却难以大尺寸制备的难题，是一种很有发展潜力的新型复合发光材料。 玻璃除了易于大尺寸制备与加工外，相对于晶体，熔化温度较低。选用低熔点玻璃为基质玻璃与高熔点晶体复合，在玻璃的熔融温度下，利用玻璃相的高温流动性，将晶体浸润包覆，赶出气体，并将晶体连接，从而可以得到较大尺寸的复合样品。另外，玻璃有较大的形成区域，组分连续可变。因此可以通过改变玻璃的组分来调整玻璃的折射率，使之与晶体的折射率相匹配，减小玻璃与晶体折射率差而导致的光散射增加复合样品的透明度。 本文以稀土掺杂的CaF2纳米晶为复合晶体，氟磷玻璃（FP）为复合基质玻璃，分别制备出了近红外发光和发白光的透明的CaF2-FP微纳复合材料，并对它进行了相关表征和测试。主要研究内容如下： 1）共沉淀制备了Yb3+:CaF2纳米晶体粉。纳米晶在溶液中的分散性良好，无明显聚沉现象。XRD显示沉淀中只有晶格略有畸变的CaF2衍射峰，无Yb2O3相，这表明Yb3+完全进入CaF2晶格。SEM显示合成的Yb3+:CaF2为粒径小于100nm的团聚颗粒。分析了颗粒团聚的形成原因。粉体的荧光谱表现出很明显的Stark分裂。 2）熔融法制备一系列不同组分的氟磷玻璃。将氟磷玻璃粉碎至1mm,结合DTA曲线研究各氟磷玻璃颗粒粉体的烧结特性。结果表明含有YF3和YbF3的玻璃颗粒烧结中出现乳白现象。分析认为乳浊由烧结过程中YbPO3 或YPO3的析出导致。选择含较少Yb2O3的玻璃系统，改变其组分中氟化物与磷酸盐的比例。结果显示氟磷玻璃折射率随组分中磷酸盐的增加而增加。选择与CaF2折射率相匹配的玻璃组成：10MgF2- 20CaF2- 20SrF2-6BaF2- 4NaF- 40AlF3-2YbF3- 7.2NaPO3- 2.8Al(PO3)3（mol%）作为复合样品的基质玻璃。 3） 熔融浇铸法制备了组成(50GeO2-20Al2O3-15CaF2-15LiF)稀土离子掺杂的锗酸盐氧氟玻璃并进行合适的微晶化热处理，得到了透明的微晶玻璃。X射线衍射表明玻璃中析出了CaF2纳米晶粒，晶粒尺寸在17 nm左右。在980 nm泵浦光的激发下，Yb3+/Er3+双掺微晶玻璃产生了蓝绿红上转换荧光。随着玻璃中Yb3+的掺杂浓度的增加蓝光和红光荧光强度增大，并且高浓度Yb3+掺杂下的Yb3+/Er3+双掺的透明陶瓷样品中出现了Yb3+离子的合作上转换发光现象。其中5 %Yb3+/1 %Er3+的微晶玻璃样品的上转换发光已经出现白光效果。为实现白光输出，制备了一系列的组成为（50GeO2–20Al2O3–15CaF2–15LiF）–xYbF3–0.01ErF3的锗酸盐微晶玻璃。当x=12时，微晶玻璃样品的上转换蓝光绿光红光组合较为接近白光。 4） 将折射率调整过的玻璃粉与Yb3+:CaF2粉体充分混合均匀，通过改变Yb3+:CaF2的颗粒尺寸、glass/ Yb3+:CaF2质量比、处理温度、优化工艺路线，成功制备了含纳米级CaF2晶体的透明度良好的复合材料。Yb3+:CaF2颗粒尺寸越小，制备透明样品所需玻璃粉体越多。且复合样品中的气泡越小，样品透明度越高。XRD图谱显示透明复合材料中有CaF2存在。EDS分析进一步证实样品由Yb3+:CaF2和氟磷玻璃两相组成。SEM形貌分析结果显示Yb3+:CaF2尺寸约5μm。复合材料的吸收光谱和荧光光谱表明，其光谱是由晶体和玻璃各自荧光谱复合叠加而成。 |
| 英文摘要 | Large volume efficient luminescent material is desired both in high-powder laser system and illumination system. Glass as a kind of conventional material is very easy to be produced into large volume and processed. Additionally, dopant can be dispersed homogeneously in glass. Therefore, glass has been used in many areas as host materials for rare earth doping. However, the inefficient luminescence of rare earth ions in glass causes energy waste which hinders its further applications. On the other hand, rare earth doped crystals also play an important role in the luminescent material field benefited from their efficient luminescence. However, large volume is difficult to obtain for most crystals, and further, there is a problem for rare earth ions to be homogeneously doped into crystals. The composite composed of glass and nano-crystals can be a solution for all the problems above. This composite having rare earth ions doped nano-crystals homogeneously dispersed in glass medium possesses the convenience to be produced into larger volume and the efficient luminescence properties of crystal. The melting temperature of glass is lower than that of crystals. At a given high temperature, in the mixture of glass and crystals, the glass melts while crystals do not. The liquid glass melt repels air between crystals and the crystals adhere to each other. As a result, after cooled down, the composite composed of glass and crystals can be produced. The glass formation region is large, which allows one to vary the composition and thus, adjust the refractive index of the glass to match that of the crystals. The matched refractive indices reduce the light scattering and permit transparent composite. In our work, rare earth doped CaF2 and flurophosphate glass were chosen to produce to the composite. The composites emitting at near-infrared wavelength and emitting white light were obtained. The micro-morphological and fluorescent properties were studied. The main work was as follows: 1） Yb3+:CaF2 was synthesized by co-precipitation. Yb3+:CaF2 particles were dispersed in the solution homogeneously. No coagulation can be observed. The XRD pattern of the precipitate showed that the precipitate was lattice-distorted CaF2 crystals. No Yb2O3 pattern was observed, which indicated the incorporation of Yb3+ ions in the CaF2.The SEM morphology showed that the synthesized CaF2 crystals were aggregated into balls less than 100nm.The emission spectrum was also detected. Stark splitting was remarkable in the precipitate. 2） Fluorphosphate glasses of varying composition were melted using conventional melting and quenching process. The glasses were milled into particles of 1mm in diameter. Their sintering properties were investigated. The particles containing YF3 and much amount of Yb2O3 turned opaque, which might caused by the crystallization of YbPO3 or YPO3. The glass containing minimum of Yb2O3 was chosen to be studied further. The refractive index of the chosen glass was adjusted by change the ratio of the fluorite to the phosphate in the glass. The index increase along with the phosphate content increasing. The refractive index of the glass of the composition: 10MgF2-20CaF2-20SrF2-6BaF2-4NaF-40AlF3-2YbF3-7.2NaPO3-2.8Al(PO3)3（mol%）was very close to that of CaF2 and was chosen to be the glass to host Yb3+:CaF2. 3） Rare-earth doped germanate glass with the glass host of the composition: 50GeO2-20Al2O3-15CaF2-15LiF was prepared by conventional melting and quenching method. Transparent glass ceramic was obtained by heat-treating the germanate glass. The XRD pattern of the glass ceramic confirmed the CaF2 precipitation in the glass matrix. The calculated size of the precipitated CaF2 crystals was 17nm. Yb3+-Er3+ co-doped germante glass ceramics showed red-green-blue up-conversion emission under 980nm excition. The red and blue emissions were enhanced when Yb3+ concentration increased. The cooperative up-conversion luminescence of Yb3+ was also observed when Yb3+ concentration was high enough. White light emission was observed in the transparent glass ceramic by heat-treating (50GeO2–20Al2O3–15CaF2–15LiF)–12YbF3–0.01ErF3 glass. 4） Yb3+:CaF2 powder was mixed completely with the glass powder of which the refractive index was very close to that of CaF2 crystal. Transparent composite was obtained after thorough study by reducing the particle size of CaF2 and changing the weigh ratio of glass/ Yb3+:CaF2 and the heat-treating temperature. Reduction of the Yb3+:CaF2 size involved more glass to produce transparent sample. The reduction was beneficial to decreasing the amount of air bubbles in the sample and hence to obtaining transparent samples. The XRD pattern confirmed the existence of the Yb3+:CaF2 in the composite.SEM morphology showed that the Yb3+:CaF2 particles in the composite were about 5μm.EDS analysis further backed up the existence of Yb3+:CaF2 in the samples. The absorption spectrum and near-infrared emission spectrum of the composite indicated the spectral consisted of two parts form the glass host and Yb3+:CaF2, respectively. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16702]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 张德亮. 稀土掺杂微纳复合材料的发光研究[D]. 中国科学院上海光学精密机械研究所. 2011. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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