| About this Abstract |
| Meeting |
MS&T21: Materials Science & Technology
|
| Symposium
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Grain Boundaries, Interfaces, and Surfaces in Ceramics: Fundamental Structure—Property—Performance Relationships
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| Presentation Title |
Size-dependent Lattice Contraction in Nano-MnO |
| Author(s) |
Michael M. Ramsdell, Jenna M. Pike, Syed Khalid, Siu-Wai Chan |
| On-Site Speaker (Planned) |
Michael M. Ramsdell |
| Abstract Scope |
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. |