Origins of high fracture toughness and glass‐like thermal conductivity in Zr–Ta–O composites

Abstract

AbstractScreening multifunctional thermal/environmental barrier coatings (T/EBCs) for ceramic matrix composites (CMCs) and alloys contribute to developing highly efficient hypersonic vehicles and aeroengines. This work elucidates that Zr–Ta–O composites are T/EBCs for Al2O3 fiber‐reinforced Al2O3 (Al2O3f/Al2O3) CMCs and alloys. Zr–Ta–O composites have superiorities of glass‐like thermal conductivity (1.4 W m–1 K–1), thermal expansion coefficients (8.6–12.3 × 10–6 K–1) matching to Al2O3f/Al2O3 and alloys, and high toughness (3.4 MPa m1/2). The origins of high toughness are elucidated from crack‐propagation models and formation of micro‐cracks, which consume lots of crack fracture energy and relieve the stress concentration of indentation tips. The long‐range‐ordered and short‐range‐disordered arrangements of cations and the highly twisting lattices of Ta2Zr6O17 significantly contribute to their glass‐like thermal conductivity. This work motivates upcoming study and application of Zr–Ta–O composites as T/EBCs with working temperature reaching 1500°C.