Atomic Scale Characterization and Modeling of Silicon Nitride/Rare-Earth Oxide Interfaces

非技术描述：由于块体氮化硅（Si 3 N4）陶瓷在许多高温应用中具有理想的机械和物理性能，因此在过去二十年中得到了广泛的研究。另一方面，Si 3 N4陶瓷的固有特性是它们的脆性（易碎性），这限制了它们作为结构部件的使用和可靠性。 已经证明，用稀土氧化物掺杂Si 3 N4的晶界降低了这种固有的脆性，并改善了其机械性能。 在该计划中，目的是通过使用先进的扫描透射电子显微镜和最先进的第一原理（无参数）计算中的结构和电子表征方法，在Si 3 N4晶界的结构-性能关系的基本原子理解中迈出重要一步。 这样的原子理解是最重要的一步，在实现一个真实的突破，在定制的机械性能的氮化硅更好的设备应用。 此外，这项工作还包括对本科生和研究生进行最先进的实验表征方法和计算建模研究的重要培训，用于研发行业。培训学生沿着实验和理论学科是一个独特的方面，拟议的活动，预计将提供更广泛的就业机会，为学生在当前竞争激烈的就业市场。 技术说明：在该计划中，PI建议使用两种最先进的实验和计算建模技术研究Si 3 N4/稀土氧化物界面的结构-性能关系：（1）扫描透射电子显微镜（STEM）中的原子分辨率Z衬度成像和电子能量损失谱（EELS），以及（2）基于密度泛函理论（DFT）的第一性原理计算。 将用于这些研究的实验方法已经被证明可以提供关于这些界面的结构、键合和组成与氮化硅材料特性之间联系的独特信息。DFT在计算材料科学中有着非常好的记录，是最广泛使用的理论工具，可以准确地研究结构和化学复杂材料的结构-性能关系。 特别是，在拟议的研究计划中，PI使用这些实验和理论技术的独特组合，旨在了解界面原子和电子结构如何受氧和不同稀土元素的尺寸/电子结构控制。 这一信息是至关重要的，以实现真实的突破，在定制的Si 3 N4的机械性能，更好的设备应用。 此外，这项工作还包括对本科生和研究生进行最先进的实验表征方法和计算建模研究的重要培训，用于研发行业。培训学生沿着实验和理论学科是拟议活动的一个重要方面，并预计将提供更广泛的就业机会，为学生在竞争激烈的就业市场。

NON-TECHNICAL DESCRIPTION: Bulk silicon nitride (Si3N4) ceramics have been investigated extensively over the last twenty years due to their desirable mechanical and physical properties in many high temperature applications. An intrinsic characteristic of Si3N4 ceramics, on the other hand, is their brittleness (fragility), which limits their use and reliability as structural components. It has been demonstrated that doping the grain boundaries of Si3N4 with rare-earth oxides decreases this intrinsic brittleness, and improves its mechanical properties. In this program, the aim is to take a significant step in a fundamental atomic understanding of the structure-property relationships of Si3N4 grain boundaries by using advanced methods of structural and electronic characterization in state-of-the-art scanning transmission electron microscopes and state-of-the-art first-principles (parameter-free) calculations. Such atomic understanding is the most important step in achieving a real breakthrough in tailoring the mechanical properties of Si3N4 for better device applications. Additionally, this work includes significant training of undergraduate and graduate students in the most advanced experimental characterization methods and computational modeling studies, used in the research and development industry. Training students along both experimental and theoretical disciplines is a unique aspect of the proposed activity, and is expected to offer a wider range of career opportunities for the students in the current competitive job market. TECHNICAL DESCRIPTION: In this program, the PIs propose to investigate the structure-property relationships in the Si3N4/rare-earth oxides interfaces using two state-of-the-art experimental and computational modeling techniques: (1) atomic-resolution Z-contrast imaging and electron energy-loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM), and (2) first principles calculations based on density functional theory (DFT). The experimental methods that will be used in these studies have already been shown to provide unique information on the link between structure, bonding, and composition of these interfaces with the material properties of silicon nitride. DFT, with this very good track record in computational materials science, is the most widely used theoretical tool to accurately study structure-property relationships in structurally and chemically complex materials. In particular, in the proposed research program the PIs, using a unique combination of these experimental and theoretical techniques, aim to understand how the interfacial atomic and electronic structures are controlled by oxygen and the size/electronic structure of the different rare-earth elements. This information is crucial in order to achieve a real breakthrough in tailoring the mechanical properties of Si3N4 for better device applications. Additionally, this work includes significant training of undergraduate and graduate students in the most advanced experimental characterization methods and computational modeling studies, used in the research and development industry. Training students along both experimental and theoretical disciplines is an important aspect of the proposed activity, and is expected to offer a wider range of career opportunities for the students in a competitive job market.