What is in a Name: Defining -High Entropy- Oxides

TL;DR

This paper clarifies the definitions and classifications of high entropy oxides, emphasizing the importance of crystallinity, composition, and mixing scales for understanding these complex materials.

Contribution

It provides a unified framework and common language for classifying and understanding high entropy oxides across physics, chemistry, and materials science.

Findings

Distinguishes between compositionally complex, high entropy, and entropy stabilized oxides.

Highlights the importance of crystallinity and mixing scales in defining these materials.

Proposes a classification framework to unify terminology across disciplines.

Abstract

High entropy oxides are emerging as an exciting new avenue to design highly tailored functional behaviors that have no traditional counterparts. Study and application of these materials are bringing together scientists and engineers from physics, chemistry, and materials science. The diversity of each of these disciplines comes with perspectives and jargon that may be confusing to those outside of the individual fields, which can result in miscommunication of important aspects of research. In this perspective, we provide examples of research and characterization taken from these different fields to provide a framework for classifying the differences between compositionally complex oxides, high entropy oxides, and entropy stabilized oxides, which is intended to bring a common language to this emerging area. We highlight the critical importance of understanding a materials crystallinity, composition, and mixing length scales in determining its true definition.