High wave transmittance and low thermal conductivity Y–α-SiAlON porous ceramics for high-temperature radome applications

With the development of hypersonic vehicle technology, ceramic-based radome materials are highly demanded due to their high operating temperatures, good dielectric properties, and high mechanical properties. Although α-SiAlON is an ideal material for radome applications, its intrinsic low transmittance and high thermal conductivity limit its applications. Herein, we prepared Y–α-SiAlON porous ceramics through tert-butanol (TBA) gel-casting using the self-synthesized α-SiAlON powder. The Y–α-SiAlON porous ceramics exhibited a uniform micron-level connected pore structure with the porosity (P) of 44.2%–58.6%. The real part of permittivity (ε ¢) was 3.13–4.18 (8.2–12.4 GHz), which decreased significantly with the increasing porosity. The wave transmittance 2 (|T |) of the sample with porosity of 58.6% could exceed 80% in the thickness range of 6–10 mm. The thermal conductivity was maintained at a low level of 1.38–2.25 W·m^−1·K−1 owing to the introduction of the pore structure. The flexural strength was 44.73–88.33 MPa, which may be increased by rod-like α-SiAlON grains. The results indicate that the prepared Y–α-SiAlON porous ceramics meet the requirements of high-temperature wave-transmitting materials for radome applications.