|About this Abstract
||MS&T23: Materials Science & Technology
||Phase Transformations in Ceramics: Science and Applications
||Structural Evolution of MgAl2O4 and NiAl2O4 Disordered Spinel Oxides Studied via In Situ Neutron Total Scattering
||John M. Hirtz, Eric C O'Quinn, Igor Gussev, Joerg C Neuefeind, Maik Lang
|On-Site Speaker (Planned)
||John M. Hirtz
Complex oxides that adopt the isometric spinel structure (AB2O4) are regularly used in energy storage technologies. Using neutron total scattering experiments at the Spallation Neutron Source (Oak Ridge National Laboratory), we elucidated both the long-range repeating structure and the short-range local atomic arrangements of disordered and defective spinels. We have characterized MgAl2O4 and NiAl2O4 disordered through chemical substitution (Mg1-xNixAl2O4), external heating (up to 1000°C), and dense electronic excitation through swift heavy ion irradiation (2.2-GeV Au ions). Locally, the isometric Fd3 ̅m spinel structure re-arranges to a tetragonal P4122 atomic configuration with changes in chemistry or during heating to maintain local charge balance, consistent with Pauling’s rules. Interestingly, this behavior is distinct from spinels that are irradiated with swift heavy ions. In this case, the resulting defect structure includes also cations trapped at sites that are ordinarily unoccupied when the structure is disordered by chemical substitution or high temperature.