Discovery of a reversible redox-induced order-disorder transition in a 10-cation compositionally complex ceramic

TL;DR

This paper reports a reversible order-disorder transition in a 10-cation complex ceramic induced by redox conditions, altering its structure and thermal properties, and demonstrating a new method to tailor complex oxide materials.

Contribution

It introduces a novel redox-induced order-disorder transition in a high-entropy ceramic, expanding control over its structural and functional properties.

Findings

Reversible ODT observed in a 10-cation ceramic.

Structural phase remains a single-phase high-entropy solid solution.

Thermal conductivity is affected by the ODT.

Abstract

This study discovers a reversible order-disorder transition (ODT) in a 10-cation compositionally complex ceramic, (Nd0.15Pr0.15Dy0.8Ho0.8Er0.8Ti0.2Yb0.1Hf0.1Zr0.1Nb0.8)O7-delta, induced via annealing in oxidized vs. reduced environments at 1600C. Notably, the 10-cation oxide remains a homogenous single-phase high-entropy solid solution before and after the ODT in the pyrochlore vs. fluorite structure that can be quenched. In-situ neutron diffraction reveals the oxygen vacancy formation and atomic displacement during this ODT. The temperature dependence of thermal conductivity is altered by the ODT. This study reveals a new pathway to induce ODT via a redox transition to tailor the properties of compositionally complex fluorite-based oxides.