Phase Separation and Fluorescence Properties of Rare-Earth Doped Borosilicate Glasses

目前，人们对具有优异光学性能和适合光子应用的材料有很高的需求。本研究的重点是利用na20 - b2o3 - sio2模型体系，制备和表征在被硅酸盐基质包围的富硼酸盐液滴中显示相分离的荧光硼硅酸盐玻璃。因此，应该保护富含硼酸盐的液滴免受硅酸盐基质的化学侵蚀和降解。由于液滴相的数量可以调节到30%以上，因此其中一个玻璃相中稀土离子的浓度将显著提高。硼硅酸盐玻璃的微观结构应通过热处理来调整，从而形成尺寸、尺寸分布和元素分布不同的相分离结构。荧光特性，即荧光强度、发射波长和荧光寿命，将通过控制各自相的大小和组成来定制。本项目的主要目的之一是了解相分离含稀土硼硅酸盐玻璃的玻璃结构和组成对荧光性质的影响。因此，Na2O将部分或全部被不同的碱或碱土氧化物，如K2O、Cs2O、SrO或BaO所取代，并将研究对相分离的影响，特别是对形成结构的影响。为了获得不同的结构玻璃参数，如玻璃的网络连通性、结构单元和光学碱度，还需要改变B2O3/SiO2的比例。由于光学碱度直接影响稀土离子的局部位置，因此会影响其发光性能。铸态和热处理样品的纳米和微观结构将使用电子显微镜分析进行全面研究。此外，微观结构将分析尺寸、尺寸分布、形状和液滴数量作为所提供温度/时间计划的函数。将特别注意有关元素分布和化学梯度的信息。由于在稀土掺杂玻璃中，荧光性质在很大程度上取决于发光离子的配位、浓度和空间分布，因此需要应用拉曼光谱、红外光谱和核磁共振光谱等结构表征技术来了解稀土离子掺入这些玻璃中的基本情况，并将荧光性质与结构排列联系起来。结构表征技术和发光测量的结合将显著增强对荧光性质和玻璃结构之间关系的共同理解。这些结论将有助于开发新的光学材料。

Nowadays, there is a high demand for materials possessing excellent optical properties and which are suitable for photonic applications. This proposal focuses on the preparation and characterization of fluorescent borosilicate glasses showing phase separation in borate-rich droplets surrounded by a silicate matrix, using the model system Na2O-B2O3-SiO2. Hence, the borate-rich droplets should be protected against chemical attack and degradation by the silicate matrix. Since the quantity of the droplet phases can be adjusted to be more than 30 %, the concentration of the rare-earth ions incorporated in one of the glassy phases will be significantly higher. The microstructure of the borosilicate glasses shall be adjusted by heat treatments leading to phase separation structures which vary in size, size distribution as well as the elemental distribution. The fluorescence properties, i.e. fluorescence intensity, emission wavelength, and fluorescence lifetimes, will be tailored by controlling size and composition of the respective phases. One of the main purposes of this project is to develop a general understanding of the influence of glass structure and composition of phase separated rare-earth containing borosilicate glasses on the fluorescence properties. Therefore, Na2O will be partially or totally replaced by different alkali or alkaline earth oxides, such as K2O, Cs2O, SrO, or BaO, and the effect on phase separation, especially on the formed structures will be studied. In order to obtain different structural glass parameters, such as network connectivity, structural units, and optical basicity of the glasses, the B2O3/SiO2 ratio shall be also varied. Since the optical basicity directly affects the local sites of the rare-earth ions, the luminescence properties will be influenced. The nano- and microstructure of the as-cast and heat treated samples will be comprehensively studied using electron microscopic analyses. Furthermore, the microstructure will be analyzed regarding size, size distribution, form, and number of droplets as a function of the supplied temperature/time schedule. Special attention will be paid to information about element distributions and chemical gradients. Since in rare-earth doped glasses, the fluorescence properties strongly depend on the coordination, concentration, and spatial distribution of luminescent ions, structural characterization techniques such as Raman, IR, and NMR spectroscopy shall be applied to gain a fundamental understanding of the rare-earth ion incorporation into these glasses and correlate the fluorescence properties to structural arrangements. The combination of structural characterization techniques and luminescence measurements will remarkably enhance the common understanding of the relationship between fluorescence properties and glass structure. These conclusions will help to develop new optical materials.