Size Disorder as a Descriptor for Predicting Reduced Thermal Conductivity in Medium- and High-Entropy Pyrochlores

TL;DR

This study demonstrates that a modified size disorder parameter effectively predicts reduced thermal conductivity in medium- and high-entropy pyrochlores, aiding the design of thermally-insulative ceramics with retained stiffness.

Contribution

It introduces a modified size disorder descriptor that correlates with thermal conductivity reduction in entropy ceramics, guiding their design for thermal insulation.

Findings

Achieved up to 35% reduction in thermal conductivity.

Thermal conductivity correlates with the modified size disorder parameter.

Maintained Young's modulus despite thermal conductivity reduction.

Abstract

High-entropy ceramics generally exhibit reduced thermal conductivity, but little is known about what controls this suppression and which descriptor can predict it. Herein, 18 medium- and high-entropy pyrochlores were synthesized to measure their thermal conductivity and Young's modulus. Up to 35% reductions in thermal conductivity were achieved with retained moduli, thereby attaining insulative yet stiff properties for potential thermal barrier coating applications. Notably, the measured thermal conductivity correlates well with a modified size disorder parameter. Thus, this modified size disorder parameter is suggested as a useful descriptor for designing thermally-insulative medium- and high-entropy ceramics (broadly defined as "compositionally-complex ceramics").