Simultaneously reduced thermal expansion coefficients and conductivity of SiO₂–AlTaO₄ oxides with the enhanced toughness

Directional optimization of properties is of significant interest for various protective coatings materials. This study investigates the effects of SiO 2 doping on AlTaO 4 ceramics as environmental barrier coatings (EBCs), and the changes in crystal structure and comprehensive properties are thoroughly investigated. The x mol% SiO 2 –AlTaO 4 (SATO, x = 0, 3, 6, 9, 12, 15) ceramics are fabricated via a solid‐state sintering process, and their structures, as well as thermo‐mechanical properties, are systematically analyzed. The results reveal that SiO 2 doping introduces point defects and lattice distortions, which significantly reduce the thermal conductivity by 44% at 900°C, and effectively suppresses the increase in thermal conductivity at elevated temperatures. Furthermore, the fracture toughness is improved from 3.01 to 3.38 MPa·m 1/2 , demonstrating superior mechanical properties compared with other EBC materials. The thermal expansion coefficients (TECs) are reduced to 5.71 × 10 −6 K −1 at 1200°C, which match with those of SiC ceramic matrix composites (TECs = 5.50 × 10 −6 K −1 ). These findings highlight that SATO ceramics are promising candidates as EBC materials, and SiO 2 doping can further advance its high‐temperature applications.