Effect of Cristobalite Content on Physical, Dielectric Constant, and Bending Strength of Fused Silica Ceramics Formed by Slip Casting Method

Fused silica ceramics are widely used in electronics and aerospace industries. In the present study, 70 µm of fused silica powder was milled to 10 µm through fast milling. The appropriate slurry was prepared for slip casting with the powder-to-water ratio of 80:20. After drying the specimens, the samples were sintered at different temperatures of 1100 °C to 1400 °C. The density increased upon increasing the temperature from 1.79 to 1.98 g/cm3. The phase transformation of the samples was investigated using XRD. The structure of the samples was analyzed using FTIR, and their microstructure was examined using a Field Emission Scanning Electron Microscope (FESEM). The bending strength of the samples was measured using the three-point method. According to the results, the cristobalite phase increased upon increasing the sintering temperature. The best flexural strength value (48.7 MPa) was obtained for the sample sintered at 1300 °C. The dielectric constants of the fused silica ceramics were about 3-3.8 in the frequency range of 8 to 12 GHz.