Sieun and Peter both gave contributed talks on entropy-stabilized oxides at ACerS EMA 2020 in Orlando last week.
Tunability of native defect density through local configuration-controlled disorder in entropy-stabilized oxides
Abstract: Entropic stabilization has become a strategy to create new oxide materials and novel properties, however, achieving an atomistic understanding of these properties has been challenged by the local compositional and structural disorder that underlies their fundamental structure-property relationships. Here, we combine high-throughput atomistic calculations, machine-learning algorithms, and experimental characterization to investigate the role of local configurational and structural disorder on the thermodynamics of intrinsic point defects in (MgCoNiCuZn)O-based entropy-stabilized oxides (ESOs) and their influence on the electrical properties. From theory, we find that the cation-vacancy formation energy decreases with increasing local tensile strain, while oxygen-vacancy formation depends on the local structural distortion associated with the local configuration of chemical species. Through relatively small changes in the mole fraction of cations, the equilibrium defect density can be tuned by over two orders of magnitude. Vacancies in ESOs exhibit deep thermodynamic transition levels leading to transport via variable range hopping. Our results motivate tuning local structural distortions by local alloy composition as an engineering principle to enable controlled defect formation in multi-component oxides.
Electronic and magnetic interplay in entropy stabilized oxide thin films
Abstract: A unique benefit to entropic stabilization is the increased solubility of elements, which opens a broad compositional space with subsequent local A unique benefit to entropic stabilization is the increased solubility of elements, which opens a broad compositional space with subsequent local chemical and structural disorder resulting from different atomic sizes and preferred coordinations of the constituents. In the antiferromagnetic entropy-stabilized oxides studied here, we see that by tuning the chemistry, and thus the concentration of local structural distortions, we can either induce or reclaim a large degree of frustration in the magnetic lattice of the material. As the large dielectric response of these materials may be strongly linked to their structure, here we study the interplay of electronic and magnetic functional responses in entropy-stabilized oxides. Our results reveal that the unique characteristics of entropy stabilized materials can be utilized to engineer and enhance magnetic functional phenomena in oxide thin films, as well as offer a powerful platform for the study of defects and functional properties.