Exploring the Mechanical and Thermophysical Potential of Novel Lanthanum Aluminate–Yttria‐Stabilized Zirconia Composites for Thermal Barrier Coatings

ABSTRACT In this study, a novel composite strategy was developed by combining 8 wt.% yttria‐stabilized zirconia (8YSZ) with lanthanum aluminate (LaAlO 3 ) to form a ferroelastic‐ and transformation‐toughened dual‐phase composite, aiming to evaluate its feasibility as thermal barrier coatings (TBCs). The LaAlO 3 ‐8YSZ composites across a complete composition range were fabricated via solid‐state sintering and systematically characterized for their phase evolution, microstructure, mechanical properties, and thermophysical performance. The optimal composition demonstrates a remarkable fracture toughness of 6.6 MPa·m 1/2 , a high thermal expansion coefficient of 11.09 × 10 −6 K −1 , and a thermal conductivity of 2.5 W·m −1 ·K −1 at 1000°C, which is comparable to that of 8YSZ. Especially, synergistic toughening mechanisms were elucidated, including residual stress toughening from coefficient of thermal expansion mismatch, stress‐induced phase transformation, and crack deflection promoted by a refined and interlocking two‐phase microstructure. Furthermore, analysis using the Maxwell‑Garnett model elucidated the thermal transport mechanisms, providing guidance for further optimization. This work demonstrates that the LaAlO 3 ‐8YSZ composites offer a well‐balanced and high‐performance material candidate for next‐generation TBCs.