|About this Abstract
||Materials Science & Technology 2019
||Phase Transformations in Ceramics: Science and Applications
||Phase transitions in hollandite oxides with nanoscale chemical ordering
||Scott Misture, Robert Koch, Jake Amoroso, Kyle Brinkman, Mingyang Zhao
|On-Site Speaker (Planned)
The structures of most multicomponent oxides have been described using traditional crystallography. However, some oxides demonstrate nanoscale chemical ordering, which must be described using supercell models to define the chemical clustering.
We have recently discovered nanoscale chemical clustering in hollandite oxides, which contain 1-D tunnels that accommodate guest ions and are of high interest in nuclear waste sequestration, particularly for 137Cs entrapment. We have studied for example Al/Ti in Ba0.33Cs1.0Al1.67Ti6.33O16, as well as the bulk phase transitions that occur on heating. X-ray pair distribution functions were modeled using supercells in a Reverse Monte Carlo approach, complemented by high temperature laboratory powder diffraction. Thus we describe the nanoscale ordering above/below phase transitions, as well as during synthesis, and find clear connections to Cs ion release rates. DFT models and thermodynamic measurements of stability strengthen arguments about the importance of nanoscale disorder.
||Definite: At-meeting proceedings