High entropy oxides: The role of entropy, enthalpy and synergy

This viewpoint article focuses on some of the important issues related to the emerging field of high entropy oxides (HEOs). Open queries regarding the role of entropy, enthalpy, individual elements and synergy arising from the presence of multiple elements in HEOs are discussed. In addition, a brief overview of the current state of research on HEOs is provided. Finally, we share our views on the uniqueness of HEOs by describing some features, which distinguish them from the conventional oxides. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.