Isotopic Effects, Jump Correlation and Diffusion Paths in Li-containing Oxide Glasses

本子项目着重于系统研究锂在非晶态和晶体氧化相中的化学扩散和自扩散。扩散偶实验将用于研究锂在化学均质材料和具有化学势梯度的系统中的扩散。元素和同位素扩散曲线将使用结合激光烧蚀（MC-ICP-MS和Sektorfeld-MS）的质谱测量，然后使用扩散方程进行数学处理。锂离子在氧化玻璃中的迁移机制尚不清楚，因此这类材料是本研究的核心。通过对单晶和玻璃的比较，以及其他结构修饰，可以深入了解短序和长序对锂扩散的影响。我们在第一个项目期间对硅酸盐和铝硅酸盐的研究结果将通过纳入对其他共价键含量高的氧化物体系（即硼酸盐和磷酸盐）的研究来扩展。玻璃的结构变化可以通过改变冷却速率引起。低密度可以通过在环境压力下快速淬火来实现，例如使用滚柱淬火技术，而高密度可以通过在高压下缓慢冷却来实现。阻抗谱结合扩散实验得到的结果可以精确地表征影响锂迁移率的相关因素。固体材料的相关系数是由缺陷和潜在的景观决定的。解释实验得到的相关系数在非晶系统是具有挑战性的。在这方面，理论建模将有助于确定锂扩散的主要机制。固体量子化学和经典计算将在具有周期性超级单体的简单模型系统上进行，这些超级单体代表了玻璃的结构特征。该项目的主要目标之一是发展理论来预测材料组成和局部结构的扩散特性。首先，模型将描述在第一个项目期间（硅酸盐和铝硅酸盐）研究的系统中的扩散行为。之后，建模概念将应用于其他系统，以确定锂迁移率的基本约束。随后，将对模型概念进行实验测试，以详细说明预测含锂玻璃扩散行为的可能性。

The subproject focuses on systematic investigation of the chemical diffusion and self-diffusion of lithium in amorphous and crystal oxide phases. Diffusion couple experiments will be used to study lithium diffusion in chemically homogenous materials and in systems with a chemical potential gradient. The elemental and isotopic diffusion profiles will be measured using mass spectroscopy coupled with laser ablation (both MC-ICP-MS and Sektorfeld-MS) and then mathematically processed using diffusion equations. Li-migration mechanisms are insufficiently understood in oxide glasses and thus such materials stand in the core of this study. The comparison between single crystals and glasses, as well as other structural modifications yields insight into the impact of short- and long-range order on Li-diffusion. The results of our studies of silicates and aluminosilicates in the first project period shall be expanded by incorporating investigations on other oxide systems with the high content of covalent bonding, namely borates and phosphates. Structural variations in glasses can be induced by varying the cooling rate. Lower densities will be achieved through rapid quenching at ambient pressure, e.g. using a Roller-Quenching technique, while the higher densities can be achieved by slow cooling at high pressures. The results obtained by impedance spectroscopy combined with the diffusion experiments allow precisely characterizing the correlation factors affecting Li-mobility. The correlation coefficient in solid state materials is determined by defects and by the potential landscape. The interpretation of experimentally obtained correlation coefficients in amorphous systems is challenging. In this respect theoretical modelling will help in identifying the dominant mechanisms of Li-diffusion. Solid state quantum chemical and classical calculations will be performed on simple model systems with a periodical supercell representing structural features of glasses. One of the principal goals of this project is to develop theories to predict the diffusion properties in function of the composition and the local structure of the materials. Firstly, models will be to describe the diffusion behaviour in systems studied in the first project period (silicates and aluminosilicates). Afterwards, the modelling concept will be applied to other systems to identify fundamental constraints on Li-mobility. Subsequently, the modelling concepts will be experimentally tested to elaborate possibilities for prediction of diffusion behaviour of Li-bearing glasses.