MRI: Acquisition of Equipment for Thermal and Optical Studies of Sol-gel Materials Containing Rare Earth Ions

MRI：购置用于含稀土离子溶胶-凝胶材料的热和光学研究的设备

• 批准号: 0421023
• 负责人: Daniel Boye
• 金额: $ 12万
• 依托单位: Davidson College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0421023&HistoricalAwards=false
• 关键词: MRI; Acquisition; Equipment; Thermal; Optical

Sol-gel synthesis provides a low temperature means for preparing optically transparent amorphous materials that are safer, more energy efficient and more cost effective to produce than traditional glasses made by thermally quenching molten material. One attractive aspect of sol-gel synthesis is that the optical properties of a dry gel that has been annealed to temperatures near ~1000 C approach that of a melt glass of similar composition. Sol-gel materials doped with rare earth (RE) ions are used in many optical applications including lasers, environmental and biological sensors, solar concentrators, active waveguides, phosphors and other photonic materials. The incorporation RE ions in sol-gels is interesting from a fundamental standpoint because information about the nature of the host, and how the host and RE exchange energy, may be gained by studying the host's influence on the optical properties of the RE ion. A more complete understanding of the relevant energy transfer interactions is needed. Previous work has concentrated on spectroscopic studies of either dried gels or fully annealed glasses. In contrast, this project proposes to correlate optical behavior with changes in the RE environment as the material is processed from dried gel to glass. Thermodynamic measurements during the evolution of the sol-gel materials will provide information about the host composition and structure, and an applied external electrical field will be used to modify the RE local environment by controlling the presence and motion of free ions within the material. With this information, it is hoped that the optical properties can be improved so that these materials may find greater practical application. This undergraduate research project will study sol-gel materials containing rare earth (RE) ions. The sol-gel process is a low temperature method for preparing transparent media that may easily be doped with a variety of optically active elements. Sol-gel materials doped with RE ions are used in many applications including lasers, environmental and biological sensors, solar concentrators, active waveguides, phosphors and other photonic materials. Two issues have been identified that limit the fluorescence yield of sol-gel materials doped with optically active RE ions: the presence of hydroxyl groups provides non-radiative pathways via multi-phonon relaxation, and the clustering of RE ions facilitates both energy migration and cross relaxation. This project will follow new lines of inquiry to address these important problems. Thermodynamic measurements during the evolution of the sol-gel materials, such as simultaneous differential scanning calorimetry and thermogravimetric analysis, will provide information about the host composition and structure as a dry gel densifies upon heating. Further, an applied external electrical field will be used to modify the RE local environment by controlling the presence of free ionic components. At all stages in the synthesis process, RE spectroscopy will be used to probe the materials, providing information that complements the knowledge gained from the thermal and electrical experiments. After the sol-gel materials are fully densified, the nature of energy transfer interactions among RE ions will be investigated with time-resolved spectroscopic measurements and with spectral hole burning, a high resolution saturation spectroscopy technique. It is hoped that through these studies the quantum yield and other optical properties of these materials can be improved.

SOL-GEL合成提供了一种低温手段，用于制备光学透明的无定形材料，这些材料比通过热淬火熔融材料制成的传统玻璃更安全，更节能且具有更高的成本效益。 溶胶 - 凝胶合成的一个有吸引力的方面是，已退火到接近约1000 C的温度接近的干凝胶的光学特性接近了类似成分的熔体玻璃。 用稀土离子掺杂的溶胶 - 凝胶材料用于许多光学应用中，包括激光器，环境和生物传感器，太阳能集中器，活性波导，磷光体和其他光子材料。 从基本的角度来看，Sol-Gels中的融合很有趣，因为有关宿主性质的信息以及宿主和重新交换能量如何通过研究宿主对RE离子的光学特性的影响来获得。 需要对相关的能量转移相互作用进行更完整的了解。 先前的工作集中在干凝胶或完全退火的玻璃的光谱研究上。相比之下，该项目提议将光学行为与RE环境的变化相关联，因为该材料从干凝胶到玻璃处理。 Sol-Gel材料演变过程中的热力学测量将提供有关宿主组成和结构的信息，并且将使用应用的外部电场来通过控制材料中的自由离子的存在和运动来修改RE局部环境。有了这些信息，希望可以改进光学性能，以便这些材料可以找到更大的实际应用。 该本科研究项目将研究含有稀土离子的溶胶 - 凝胶材料。 Sol-Gel工艺是制备透明介质的低温方法，可以很容易地用各种光学活性元素掺杂。 掺杂离子的溶胶 - 凝胶材料用于许多应用，包括激光器，环境和生物传感器，太阳能集中器，主动波导，磷光体和其他光子材料。 已经确定了两个问题，这些问题限制了掺杂光活性的离子掺杂的溶胶 - 凝胶材料的荧光产量：羟基的存在通过多声片松弛提供非辐射途径，而Re离子的聚集促进了能量迁移和交叉放松。 该项目将遵循新的询问线，以解决这些重要问题。 Sol-Gel材料演变过程中的热力学测量值，例如同时进行差扫描量热法和热重分析，将提供有关宿主组成和结构的信息，作为干凝胶在加热时致密。 此外，通过控制自由离子组件的存在，将使用应用的外部电场来修改RE局部环境。 在合成过程中的所有阶段，将使用RE光谱探测材料，提供补充从热和电气实验中获得的知识的信息。在完全致密的溶胶 - 凝胶材料完全致密之后，将通过时间分辨的光谱测量和光谱孔燃烧（一种高分辨率饱和光谱技术）研究RE离子之间的能量传递相互作用的性质。 希望通过这些研究，可以改善这些材料的量子产率和其他光学特性。