High-entropy (Ho0.2Y0.2Dy0.2Gd0.2Eu0.2)2Ti2O7/TiO2 composites with excellent mechanical and thermal properties

High-performance ceramics with low thermal conductivity, high mechanical properties, and idea thermal expansion coefficients have important applications in fields such as turbine blades and automotive engines. Currently, the thermal conductivity of ceramics has been significantly reduced by local doping/substitution or further high-entropy reconfiguration of the composition, but the mechanical properties, especially the fracture toughness, are insufficient and still need to be improved. In this work, based on the high-entropy titanate pyrochlore, TiO2 was introduced for composite toughening and the high-entropy (Ho0.2Y0.2Dy0.2Gd0.2Eu0.2)2-Ti2O7-xTiO2 (x = 0, 0.2, 0.4, 1.0 and 2.0) composites with high hardness (16.17 GPa), Young's modulus (289.3 GPa) and fracture toughness (3.612 MPa & BULL;m0.5), low thermal conductivity (1.22 W & BULL;m- 1 & BULL;K-1), and thermal expansion coefficients close to the substrate material (9.5 x10-6/K) were successfully prepared by the solidi-fication method. The fracture toughness of the composite toughened sample is 2.25 times higher than that before toughening, which exceeds most of the current low-thermal conductivity ceramics.