Grain Boundaries, Interfaces, and Surfaces in Ceramics: Fundamental Structure—Property—Performance Relationships: Atomistic Approaches
Sponsored by: ACerS Basic Science Division, ACerS Electronics Division
Program Organizers: Rheinheimer Wolfgang, Forschungszentrum Jülich; Catherine Bishop, University of Canterbury; Shen Dillon, University of California, Irvine; Ming Tang, Rice University; John Blendell, Purdue University; Wayne Kaplan, Technion - Israel Institute of Technology; Melissa Santala, Oregon State University
Monday 10:00 AM
October 18, 2021
Room: B244/245
Location: Greater Columbus Convention Center
Session Chair: Amanda Krause, University of Florida; Wayne Kaplan, TECHNION
10:00 AM Invited
Hetero-epitaxial Relationships and Atomic Structure at Ag/Ni Interfaces: Dominique Chatain1; Paul Wynblatt2; Velimir Radmilovic3; Ulrich Dahmen4; 1CNRS; 2Carnegie Mellon University; 3University of Belgrade; 4Lawrence Berkeley National Laboratory
The orientation relationship (OR) of a film on a single-crystal substrate is essential for a fundamental understanding of the factors that control thin film growth and texture. Among the several parameters which govern the OR, we concentrate on the role of terraces, steps and defects to accommodate structural differences or lattice mismatch across the hetero-interface between the two abutting phases.The different definitions for the heteroepitaxial relationship at an interface depend on whether the interface is considered from a surface science, a phase transformation or a grain boundary perspective.We propose an optimal choice based on the study of Ag on more than 200 Ni(hkl) surfaces.
10:40 AM
Size-dependent Lattice Contraction in Nano-MnO: Michael Ramsdell1; Jenna Pike2; Syed Khalid3; Siu-Wai Chan1; 1Columbia University; 2OxEon Energy, LLC; 3Brookhaven National Laboratory
Manganosite (MnO) nanocrystals ranging from 22 to 36 nm have been prepared by reducing hausmannite (Mn3O4) nanocrystals with hexamethylenetetramine (C6H12N4) in a heated, H2/N2 gaseous environment. X-ray Diffraction analysis indicates that the lattice parameter decreases by up to 0.18% (4.4379 Å) as the crystalline diameter decreases to 23 nm. X-ray Absorption Near Edge Spectroscopy demonstrates increasing Mn3+ fraction from 8.9% for 36 nm diameter crystallites to 14.5% for 23 nm diameter crystallites. Thus, the lattice contraction could be due in part to the decrease of the relative cation radii from Mn2+ to Mn3+. Yet, straight calculations of lattice parameter from the Mn3+ concentrations yield a 10x larger lattice contraction. We suspect the magnetic properties of the nano-MnO plays a role since most oxides show a lattice expansion due to surface adsorbents. Though it is expected that the band gap should increase with decreasing size, the increasing concentration of Mn3+ would result in states inside the bandgap, potentially giving the appearance of a smaller bandgap.