Microstructure, mechanical and high-temperature dielectric properties of zirconia-reinforced fused silica ceramics

Zirconia-reinforced fused silica ceramics were prepared using a low-toxic gelcasting method followed by pressureless sintering. The effect of zirconia addition on the microstructure, mechanical strength, thermal shock resistance, room temperature and high-temperature dielectric properties of the fused silica ceramics was investigated. The experimental results demonstrated that the mechanical strength was highly dependent on the ceramic microstructure and addition of zirconia significantly improved the mechanical strength of the resulting fused silica ceramics. The flexural strength of the fused silica ceramics containing 10 wt% zirconia sintered at 1275 °C attained 97.6 MPa, exhibiting an increase of 31.5% over that of the pure silica. The room temperature dielectric constant of the fused silica ceramic products increased slightly with increased zirconia content. However, the dielectric loss decreased with the zirconia content. More importantly, zirconia appeared to provide little impact on the excellent high-temperature dielectric properties of fused silica ceramic products.