Comprehensive Mechanical Properties of Oxide Ceramics Measured by Nanoindentation: RE3TaO7 (RE=La, Sm, Eu, Gd, Dy, Lu) as a Study Case

• • RE3TaO7 ceramics exhibit hardness (H) of 5.8–14.9 GPa and elastic modulus (E) of 127.5–247.8 GPa, enabling resistance to high-speed particle impact and thermal stresses in TBC applications. • • Fracture toughness (KC) of RE3TaO7 ranges from 1.0 to 2.0 MPa·m1/2, exceeding RE2Zr2O7 (1.0–1.5 MPa·m1/2), due to weberite structure promoting crack deflection and energy dissipation. • • Wear resistance parameter MDP (0.55–0.67) for RE3TaO7 is superior to RE2Zr2O7, indicating enhanced durability in abrasive environments. • • The selection of KC calculation method depends on l/α ratio: Eq. (3) for l/α < 1 and Eq. (4) for l/α > 1; the indentation energy method is invalid for brittle ceramics due to cracking, ensuring accurate mechanical property assessment.