Ultrafine-grained high-entropy zirconates with superior mechanical and thermal properties

Ultrafine-grained (Sm0.2Gd0.2Dy0.2Er0.2Yb0.2)(2)Zr2O7 high-entropy zirconates with single fluorite structure have been fabricated by high-pressure sintering of the self-synthesized nanopowders for the first time. The as-sintered samples exhibit a good microstructure with a grain size of 220 nm and a relative density of 96.8%, which yield excellent comprehensive mechanical properties with a high Vickers hardness of 12.5 GPa and a high fracture toughness of 3.4 MPa.m(1/2). In addition, the as-sintered samples possess a good thermostability with the grain growth rate of 30 nm/h, and a low thermal conductivity of 1.57 W.m(-1).degrees C-1 at room temperature. The superior mechanical and thermal properties are primarily attributed to the "high-entropy" and grain-refinement effects and good interface bonding. (c) 2022 The Authors. Published by Elsevier B.V. on behalf of The Chinese Ceramic Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).