Phase Stability and Thermal Transport in Yttria-Stabilized Zirconia: A Challenge for First-Principles Theory

开发具有特定用途的最佳性能组合的创新物质在科技进步中起着关键作用。不幸的是，寻找新材料是一项乏味而昂贵的任务，其中的进展通常只能通过昂贵的原型和扩展的测试系列来实现。自然，需要发展计算方法，以快速和经济有效的方式帮助和指导此类研究。在过去的几十年里，这个领域取得了巨大的进步：最值得注意的是，从头算方法的发展使得仅从第一原理就可以高效可靠地计算电子和原子性质。尽管如此，基于这种从头计算的宏观热力学性质的第一性原理评估在概念和计算上仍然是一项艰巨的任务，仍然是密集科学研究的主题。在这方面，最近在概念验证研究中提出了一系列方法。这些创新的从头算技术在本项目中用于评估氧化钇稳定氧化锆的热力学平衡（高相稳定性）和非平衡（低导热性）性质。由于这些特性，这种材料被用作飞机和燃气轮机的热障涂层。这种涂层保护底层合金免受燃烧过程中产生的极端温度的影响，因此可以提高整体工作温度，从而提高燃油效率。在这项研究中，我们希望揭示决定氧化钇稳定氧化锆热力学性质的原子机制。这些知识使我们能够专门操纵这种材料的相稳定性和导热性，从而为开发新的和改进的热障涂层铺平了道路。

The development of innovative substances that bear the optimal combination of properties for a certain application plays a key role in scientific and technological advancement. Unfortunately, the search for novel materials is a tedious and costly task, in which progress can typically be achieved only by expensive prototyping and extended test series. Naturally, the development of computational methods to aid and guide such research in a rapid and cost-efficient way is desirable. Over the last decades, tremendous progress has been achieved in this field: Most notably, the development of ab initio approaches allowed the efficient and reliable computation of electronic and atomistic properties from first principles alone. Still, the first-principles assessment of macroscopic thermodynamic properties on the basis of such ab initio calculations is a conceptually and computationally formidable task that is still the topic of intensive scientific research. In this regard a series of approaches has recently been proposed in proof-of-concept studies. These innovative ab initio techniques shall be used in this project to asses the thermodynamic equilibrium (high phase stability) and non-equilibrium (low thermal conductivity) properties of yttria-stabilized zirconia. Due to these properties this material is used as a thermal barrier coating in aircraft and gas turbines. Such coatings protect the underlying alloys from the extreme temperatures generated during combustions and hence allow to increase the overall operational temperature and hereby lead to a higher fuel efficiency. In this research we want to unveil the atomistic mechanisms that determine the thermodynamic properties of yttria-stabilized zirconia. Such knowledge then allows us to specifically manipulate the phase stability and the thermal conductivity of this material and thus paves the way for the development of new and improved thermal barrier coatings.