Development of β-SiAlON based ceramics for radome applications

This paper is a review article covering various methods reported on synthesis of β-SiAlON based ceramic materials and on their net-shape consolidation into radome structures. It also identifies a composition out of a wide-range β-Si6-zAlzOzN8-z (where z = 0–4.1) solid solution suitable for radome applications and discusses about various efficient methods reported on fabrication of radome structures out of these compositions. This article also covers the literature pertaining to β-SiAlON-SiO2 ceramic composites, which are considered to be materials of choice for certain high speed radome applications. Further, successful techniques employed for passivation of AlN powder against hydrolysis are also covered as this powder is one of the starting materials for both β-SiAlON and β-SiAlON-SiO2 ceramic composites. Surface passivation of AlN is necessary as it decomposes into alumina and ammonia, when it comes into contact with water during aqueous processing of SiAlON based ceramics, thereby not permitting formation of desired SiAlON phase. Finally, the important properties of various commercial radome materials together with those of β-SiAlON and β-SiAlON-SiO2 ceramic composites are also reviewed and presented in this article.