Seminar - Characterizing Disorder in High Entropy Oxides at Every Length Scale

Abstract:

The field of high entropy oxides (HEOs) flips traditional materials science paradigms on their head by seeking to understand what properties arise in the presence of profound configurational disorder. This disorder, which emerges as the result of multiple elements sharing a single crystalline lattice appears to imbue some HEOs with functional properties that far surpass their conventional analogs. However, there are significant questions surrounding the actual degree of configurational disorder, its role in stabilizing the HEO phase, and its effect on other physical properties. Grasping the true extent of the elemental disorder in HEOs requires advanced characterization across orders of magnitude in length scales - from the atomic scale to the average structure, preferably with elemental sensitivity. In my talk, I will discuss my group's efforts towards addressing these questions using x-ray and neutron methods. Our measurements extend from the nanoscale (x-ray absorption and extended x-ray absorption fine structure, both of which are sensitive to the immediate environment at each metal site) to the microscopic (scanning electron microscopy and x-ray fluorescence microscopy) to the average (bulk diffraction). Combining insights from each of these probes, we can arrive at a complete picture of the true level of disorder in a high entropy oxide.

Speaker Bio:

Dr. Alannah Hallas is an Associate Professor of Physics at the University of British Columbia, a Principal Investigator at the Blusson Quantum Matter Institute, and the Co-Director of CIFAR’s Quantum Materials Program. She completed her PhD in 2017 at McMaster University followed by a postdoctoral fellowship at Rice University. Alannah holds a Sloan Research Fellowship (2023-2025) and she was awarded the IUPAP Early Career Scientist Prize in the field of Magnetism in 2023. Alannah’s research focuses on the discovery and crystal growth of new quantum materials and their study using a range of neutron, x-ray, and muon techniques.