Design and Thermal Conduction Mechanisms of Rare-Earth Zirconate High-Entropy Ceramics with Low Photon Thermal Conductivity

Abstract

The high emissivity oxides (MnO₂, MnFe₂O₄ and MnAl₂O₄) were introduced into the (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂(Zr_0.7Ti_0.3)₂O₇ high-entropy matrix for in-situ reaction, and the rare-earth zirconate high-entropy ceramics with low photon thermal conductivity were prepared. The structures, thermal conductivities and thermal conduction mechanisms of the high-entropy ceramics were systematically studied. It was found that the MnO₂, MnFe₂O₄ and MnAl₂O₄ all undergo chemical reactions with the high-entropy matrix to form the high-entropy ceramics with a mixed phase of pyrochlore and perovskite. The incorporation of high emissivity oxides into the (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂(Zr_0.7Ti_0.3)₂O₇ matrix effectively reduced the room-temperature optical transmittance and increased the high-temperature infrared emissivity, thereby suppressing its photon thermal conductivity at high temperatures. Simultaneously, the electronic thermal conductivity also exhibited no increase. Consequently, the drastic increase in total thermal conductivity at high temperatures was effectively suppressed in the rare-earth zirconate high-entropy ceramics. This study is of great significance for the development of low thermal conductivity (wide temperature range) thermal barrier coating materials.