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

非技术描述：块状氮化硅(Si3N4)陶瓷由于在许多高温应用中具有良好的机械和物理性能，在过去的二十年中得到了广泛的研究。另一方面，Si3N4陶瓷的一个固有特征是它们的脆性(脆性)，这限制了它们作为结构部件的使用和可靠性。研究表明，在Si3N4晶界掺杂稀土氧化物可以降低这种本征脆性，提高其力学性能。在这个项目中，目标是通过使用最先进的扫描电子显微镜的结构和电子表征的先进方法和最先进的第一原理(无参数)计算，在原子对Si3N4晶界的结构-性质关系的基本理解方面迈出重要的一步。这种对原子的理解是在为更好的设备应用而定制Si3N4的机械性能方面实现真正突破的最重要的一步。此外，这项工作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，这些方法和研究用于研发行业。通过实验和理论学科对学生进行培训是拟议活动的一个独特方面，预计将在当前竞争激烈的就业市场为学生提供更广泛的职业机会。技术描述：在这个项目中，PI建议使用两种最先进的实验和计算模拟技术来研究Si3N4/稀土氧化物界面的结构-性质关系：(1)扫描电子显微镜(STEM)中的原子分辨率Z-对比度成像和电子能量损失谱(EELS)；(2)基于密度泛函理论(DFT)的第一性原理计算。这些研究中将使用的实验方法已经被证明提供了关于这些界面的结构、结合和组成与氮化硅材料特性之间的联系的独特信息。离散傅立叶变换在计算材料科学中有着良好的记录，是在结构和化学复杂材料中精确研究结构-性质关系的最广泛使用的理论工具。特别是，在拟议的研究计划中，PI利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到氧和不同稀土元素的尺寸/电子结构的控制。这些信息对于在为更好的设备应用量身定做Si3N4的机械性能方面实现真正的突破至关重要。此外，这项工作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，这些方法和研究用于研发行业。对实验和理论学科的学生进行培训是拟议活动的一个重要方面，预计将在竞争激烈的就业市场为学生提供更广泛的职业机会。

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.