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

With the development of hypersonic vehicles 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 application, its intrinsic low transmittance and high thermal conductivity limit its application. Herein, we prepared Y-α-SiAlON porous ceramics through tert-butanol gel-casting using self-synthesised α-SiAlON powder. Y-α-SiAlON porous ceramics exhibited a uniform micron-level connected pore structure with a porosity of 44.2%-58.6%. The real part of permittivity was 3.13-4.18 (8.2-12.4 GHz), which decreased significantly with increasing porosity. The wave transmittance of the sample with a porosity of 58.6% could exceed 80% in the thickness range of 6-10 mm. The thermal conductivity 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 44.75-88.33 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 application.