On the Elastic Anisotropy of the Entropy-Stabilized Oxide (Mg, Co, Ni, Cu, Zn)O

TL;DR

This study investigates the elastic properties of entropy-stabilized (Mg, Co, Ni, Cu, Zn)O, revealing high isotropy experimentally and mild anisotropy predicted by first principles, with magnetic and local structural effects influencing elastic behavior.

Contribution

It provides new insights into the elastic anisotropy of entropy-stabilized oxides through combined experimental and computational analysis, highlighting magnetic and local structural influences.

Findings

High elastic isotropy observed experimentally at ambient conditions.

Magnetic ordering affects elastic anisotropy in calculations.

Local ionic distortions contribute to isotropy in the material.

Abstract

In this paper, we study the elastic properties of the entropy-stabilized oxide (Mg, Co, Ni, Cu, Zn)O, using experimental and first principles techniques. Our measurements of the indentation modulus on grains with a wide range of crystallographic orientations of the entropy-stabilized oxide revealed a high degree of elastic isotropy at ambient conditions. First principles calculations predict mild elastic anisotropy for the paramagnetic structure, which decreases when the system is considered to be non-magnetic. When the antiferromagnetic state of CoO, CuO and NiO is accounted for in the calculations, a slight increase in the elastic anisotropy is observed, suggesting a coupling between magnetic ordering and the orientation dependent elastic properties. Furthermore, an examination of the local structure reveals that the isotropy is favored through local ionic distortions of Cu and Zn - due to their tendency to form tenorite and wurtzite phases. The relationships between the elastic properties of the multicomponent oxide and those of its constituent binary oxides are reviewed. These insights open up new avenues for controlling isotropy for technological applications through tuning composition and structure in the entropy-stabilized oxide or the high entropy compounds in general.