Preparation and characterization of high-entropy fluorite oxides (Ce0.16Zr0.16La0.16Sm0.16Nd0.16Y0.16)O2-δ with high mechanical properties

A novel 6-cationic single-phase high-entropy fluorite oxides (HEFOs) (Ce 0.16 Zr 0.16 La 0.16 Sm 0.16 Nd 0.16 Y 0.16 )O 2- δ (CZLSNYO) have been prepared by using solid-state reactions, and the structure and mechanical properties of the HEFOs were studied in depth. CZLSNYO exhibits a single-phase cubic fluorite structure with a smooth and crack-free surface and distinct grain boundaries after sintering at 1400 °C, 1500 °C and 1600 °C for 12 hours. The concentration of Ce 3+ in Ce ions is calculated to be 22.23 % ± 1.11 %, and the value of δ is 0.3519 ± 0.0176, yielding a nominal composition of (Ce 0.16 Zr 0.16 La 0.16 Sm 0.16 Nd 0.16 Y 0.16 )O 1.6481 ± 0.0176 . With the increase of sintering temperature, the average grain size of CZLSNYO initially enlarges and then reduces, and its Vickers hardness exhibits a comparable trend. By comparing with the 5-cations (Ce 0.2 Zr 0.2 La 0.2 Sm 0.2 Nd 0.2 )O 2- δ HEFOs, 6-cationic single-phase CZLSNYO sintered at 1500 °C possess large hardness (16.32 GPa) and fracture toughness (8.07 MPa m 1/2 ), since the addition of Y element increases the configuration entropy of the system, and Y has a greater hardness, resulting in a cocktail effect.