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 SiO₂ doping on AlTaO₄ ceramics as environmental barrier coatings (EBCs), and the changes in crystal structure and comprehensive properties are thoroughly investigated. The x mol% SiO₂–AlTaO₄ (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 SiO₂ 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 SiO₂ doping can further advance its high-temperature applications.