Fabrication of high-temperature resistant Y–Al–Si–O composite ceramics with enhanced mechanical/thermal/dielectric properties

Y–Si–O ceramics are widely used as good thermal barrier coatings but barely made for structural/functional bulks. In this study, we introduced Al2O3 into Y2Si2O7 ceramics by sol-gel method to form novel Y–Al–Si–O ceramics for high-temperature resistant microwave transmission application. The compositions, microstructures, mechanical, thermal and dielectric properties of the composites were investigated. The results show that density of the composites can achieve 2.4 g cm−3 with a porosity of 27.4%. The average compressive strength is 94.8 MPa, which is 113% higher than the Y2Si2O7 matrix. The strength retention rate at 1400 °C is 54.9%. Due to the bridging effect between Al2O3 particles and Y2Si2O7 matrix together with the interlock effect among Al2O3 grains, the mechanical strength is significantly enhanced. Additionally, excellent thermal property and oxidation resistance are indicated. The composites exhibit excellent dielectric properties, with average dielectric constant and loss tangent being 4.85 and 0.0016 (8.1–16.5 GHz, room temperature).