Effect of porosity on the structure and properties of β-SiAlON ceramics

Abstract

Porous SiAlON ceramics were produced by incorporating starch in the range of 0–5 wt% in a commercial grade SYALON 101 powder and pressureless sintered at 1700 °C for 4 h in nitrogen atmosphere. The crystal phase formation, microstructure, dielectric- and mechanical properties of SiAlON ceramic composites thus produced were investigated thoroughly. XRD analysis of the porous SiAlONs showed the presence of major phase β-Si5.85Al0.15O0.15N7.85 corresponding to β-Si6-ZAlZOZN8-Z (Z = 0.15) phase, in addition to yttrium aluminum silicon oxynitride and/or yttrium silicates. Transmission electron microscopy revealed the spherical and rod-like structure for yttrium aluminum silicon oxynitride and yttrium silicates at the proximity of pores, while the elongated and equiaxial structure for β-Si5.85Al0.15O0.15N7.85. In addition, the influence of structural transition and porosity on the dielectric constant and mechanical properties are discussed in detail. The consolidated porous SiAlON showed a promising combination of mechanical and dielectric properties, making them useful as candidate material for applications like electro magnetic wave transmitter, microwave based reactor, heat exchanger and many other structural applications, where conductivity, density and dielectric constant are critical.