Speaker
Description
High-entropy oxides (HEOs) extend the concept of entropy engineering from metallic alloys to ionic systems, offering a pathway to unprecedented compositionally complex materials with tunable structural and functional properties. Among these, the (AlCrTaTiNb)O2 system serves as a model to study how multiple cations can coexist at random occupation within a single oxide lattice and how such materials crystallize from the amorphous state or phase separate. A key challenge is however to experimentally access this element-specific structural information of such randomly elementary occupied crystalline lattices, that is the defining feature of high entropy materials.
In this work, we leverage suspended monolayer graphene films and ultrathin SiN membranes as ideal substrates for (scanning) transmission electron microscopy ((S)TEM) studies of ultrathin (AlCrTaTiNb)O2 HEOs down to atomic resolution. Using these platforms, we investigate the phase evolution of this archetypical HEO system in two distinct directions: first, by tracking the in-situ crystallization process from the amorphous state, and second, by subjecting the pre-crystallized high-entropy phase to electron beam irradiation to observe its stability and dynamic response.