Abstract
As an important A2B2O7-type ceramic, (La0.2Nd0.2Sm0.2Gd0.2Eu0.2)2Zr2O7 high-entropy pyrochlore possesses promising properties such as high melting point, high chemical durability, and low thermal conductivity. However, the low sintering ability limits its application in thermal barrier coating and radioactive waste immobilization. It usually needs long-term high-temperature soaking to achieve full density, but with inevitable grain growth. In this work, dense and grain-refined nanocrystalline (La0.2Nd0.2Sm0.2Gd0.2Eu0.2)2Zr2O7 ceramics were prepared with ultra-high pressure sintering (UHPS) method under 10 GPa at a low temperature of 800 °C. The densification behavior, microstructure evolution, and properties of the UHPS-ed samples were then investigated. The grain size of as-prepared (La0.2Nd0.2Sm0.2Gd0.2Eu0.2)2Zr2O7 ceramic was only 151 nm, which is 40% smaller than that of raw powder. In addition, it exhibited advantageous properties including both high hardness and aqueous durability. Plastic deformation under ultra-high pressure was believed as the dominant densification mechanism responsible for grain refinement and property improvement.
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