Enhancement of mechanical properties and toughening mechanisms in high-entropy RETaO4 (RE = Y, Gd, Yb, Dy, Sm) ceramics

Medium-high entropy RETaO 4 (RE = Y, Gd, Yb, Dy, Sm) ceramics are prepared by high-temperature solid-state reaction. Results show that doping rare earth ions into the A site improves the hardness, elastic modulus, fracture toughness, and fracture strength of the ceramics. As the solid solution components increase, hardness rises from 5.19 GPa to 7.43 GPa, elastic modulus from 55.2 GPa to 88.8 GPa, fracture toughness from 1.10 MPa·m 1/2 to 2.05 MPa·m 1/2 , and fracture strength from 31.8 MPa to 58.6 MPa. This enhancement is attributed to higher lattice distortion, increased internal energy, and stronger bonding. The proportion of transgranular fracture increases with solid solution content. Ferroelastic domain structures cause crack tip deflection, leading to greater fracture energy absorption. Furthermore, high-entropy and lattice distortion effects in (5RE 1/5 )TaO 4 ceramics promote high-density dislocation regions under stress, enhancing dislocation toughening.