Defect chemistry engineering and thermal treatment on dislocation mechanics in SrTiO3

现代功能氧化物的性质可以通过选择性地改变缺陷化学，即通过引入点缺陷来定制。这通常涉及将电荷引入晶格中。改变功能特性的另一种方法是引入位错。位错是线缺陷，其可以在氧化物中强烈带电，从而与点缺陷相互作用。近年来，这种新方法引起了越来越多的研究兴趣。有希望的概念验证表明，氧化物的功能特性，如导电性，导热性和超导性，可以通过改变位错结构来选择性地影响。陶瓷通常在高温下加工，在冷却期间，存在的点缺陷被冻结远离热力学平衡。因此，在引入的位错和陶瓷氧化物中的许多点缺陷之间不可避免地发生相互作用。因此，出现了以下科学相关的问题：1）位错和点缺陷的相互作用是否会改变力学性能，如塑性和开裂行为？2)点缺陷如何与先前引入的位错相互作用，作为温度和加热/冷却速率的函数，后者影响热力学平衡？3)线缺陷和点缺陷的静电场对固溶硬化的贡献是什么？样品缺陷化学性质的变化如何影响位错的迁移率？在这个项目中，我们的目标是回答这些问题，并阐明位错的热稳定性及其对机械性能的影响，这对位错控制功能以及组件的机械可靠性至关重要。为此，单晶SrTiO 3（具有不同的缺陷化学条件）将被用作参考材料，并且纳米/微观力学测试将在不同的温度下进行，以研究1）由点缺陷修改的位错成核和增殖。此外，2）将研究所产生的位错和点缺陷之间的相互作用对位错运动的影响。除了塑性，还将研究材料的开裂行为（裂纹形成和扩展），并考虑位错行为。

The properties of modern functional oxides can be tailored by selectively changing the defect chemistry, i.e. by introducing point defects. This usually involves the introduction of charges into the crystal lattice. An alternative approach to modifying functional properties is the introduction of dislocations. Dislocations are line defects, which can be strongly charged in oxides, thus interacting with point defects. In recent years, this new approach has attracted increasing research interest. Promising proofs-of-concept have shown that the functional properties of oxides, such as electrical conductivity, thermal conductivity, and superconductivity, can be selectively influenced by changing the dislocation structure. Ceramics are typically processed at high temperatures, with the point defects present being frozen far from thermodynamic equilibrium during cooling. For this reason, interactions inevitably occur between the introduced dislocations and the numerous point defects in ceramic oxides. Therefore, the following scientifically relevant questions arise:1) Are the mechanical properties, such as plasticity and cracking behavior, altered by the interaction of dislocations and point defects?2) How do point defects interact with previously introduced dislocations as a function of temperature and heating/cooling rate, the latter affecting thermodynamic equilibrium?3) What is the contribution of the electrostatic fields of line and point defects to solid solution hardening? How does a change in the defect chemistry of the sample affect dislocation mobility?In this project, we aim to answer these questions and shed new light on the thermal stability of dislocations and its influence on mechanical properties, which is crucial for dislocation-controlled functionality as well as mechanical reliability of components. For this purpose, single-crystalline SrTiO3 (with different conditions of defect chemistry) will be used as a reference material and nanong-/micromechanical tests will be performed at different temperatures to study 1) dislocation nucleation and multiplication modified by point defects. Furthermore, 2) the interaction between the generated dislocations and point defects affecting the dislocation motion will be investigated. In addition to plasticity, the cracking behavior (crack formation and propagation) of the materials will also be studied, taking into account the dislocation behavior.