Vacuum Si3N4 Lu2O3 Si3N4  2.5 um Si-Natoms Luatoms 1.5 nm Lu2O3 Atomic Scale Characterization and Modeling of Silicon Nitride/Rare-Earth Oxide InterfacesJuan C. Idrobo, Serdar Öğüt, University of Illinois at Chicago, DMR-0605964 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. These desirable properties, including the processing and sintering behavior, rely on the specific atomic and electronic structure at the interfaces between the silicon nitride grains and secondary phases (rare-earth oxides). See figure. The aim of this program 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. Z-Contrast image of a typical silicon nitride ceramic with Lu2O3 used as an additive.