Phase-reassembled high-entropy fluorites for advanced thermal barrier materials

Abstract

Thermal insulating materials are in high demand for heat flux regulation as they enhance energy conversion efficiency and reduce the consumption of fossil fuels. In this study, phase-reassembled high-entropy oxides (HEOs) were successfully produced via conventional solid-state reaction, and their thermophysical properties were investigated. Promising thermal barrier coating (TBC) candidates, A2B2O7 and A3B′O7 oxides, were reassembled to a single defective fluorite structure to further reduce the thermal conductivity via an entropy-stabilization strategy. The phase-reassembled HEO ceramics exhibited low thermal conductivity (1.06 W/m·K) and glass-like thermal conduction behavior owing to their highly distorted crystal structure. In addition, their compatible thermal expansion (∼9.95 × 10−6/K) suggests that the phase-reassembled HEOs are promising candidates for new thermal barrier materials. This study proposes a new strategy for reducing the thermal conductivity via phase reassemble beyond simply increasing the number of components.