Formation and mechanical properties of Y-substituted (Ce0.2Zr0.2La0.2Sm0.2Nd0.2)O2- high-entropy fluorite oxide

In this paper, in order to improve the mechanical properties of high-entropy fluorite oxides (HEFOs), five equimolar multicomponent oxides were synthesized by solid-phase reaction method by using element Y replacing one of the five cations in (Ce0.2Zr0.2La0.2Sm0.2Nd0.2)O2-δ. The substitution of La, Sm or Nd in (Ce0.2Zr0.2La0.2Sm0.2Nd0.2)O2-δ with Y element are able to form single-phase HEFOs at 1600 °C, while Ce4+ and Zr4+ replaced by Y3+ contains a large number of secondary phase. The former three components are almost dense and smooth, and all the elements are uniformly distributed with no obvious segregation and agglomeration. The Ce3+ concentration of Y-substituted Sm HEFOs is calculated to be 13.7%, yielding a nominal composition of (Ce0.2Zr0.2Y0.2Sm0.2Nd0.2)O1.6863. In addition, the HEFOs have the best mechanical properties with Vickers hardnesses, flexural strengths and fracture toughnesses of 15.12 GPa, 101.1 MPa and 7.88 MPa-mm1/2, respectively, which have potential applications in high-performance structural materials.