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

In this study, a novel composite strategy was developed by combining 8 wt.% yttria-stabilized zirconia (8YSZ) with lanthanum aluminate (LaAlO₃) to form a ferroelastic- and transformation-toughened dual-phase composite, aiming to evaluate its feasibility as thermal barrier coatings (TBCs). The LaAlO₃-8YSZ 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 LaAlO₃-8YSZ composites offer a well-balanced and high-performance material candidate for next-generation TBCs.