High-strength and low-dielectric ZrO2 reinforced fused silica ceramics by gelcasting

Herein, the fused silica ceramics integrating good mechanical and dielectric properties were successfully prepared by gelcasting and pressureless sintering by introducing ZrO 2 as reinforcement phase. After sintering at 1250 °C for 6 h, the introduced m-ZrO 2 underwent a displacive phase transformation from m-ZrO 2 to t-ZrO 2 . More importantly, some t-ZrO 2 phases were stably retained to room temperature by doping Y 2 O 3 . The ZrO 2 phases filled the irregular pores formed by micro-scale fused silica particles, which significantly increased the bulk density from 1.56 g/cm 3 for pure fused silica ceramics to 2.07 g/cm 3 for fused silica ceramics containing 20 wt% ZrO 2 . By reason of the increasing bulk density, stress-induced phase transformation toughening, microcrack toughening, and dispersion strengthening, the fused silica ceramics containing 16 wt% ZrO 2 displayed the highest flexural strength of 110.6 MPa, which was 83.4 % higher than pure fused silica ceramics. Throughout X-band, the prepared fused silica ceramics with different ZrO 2 contents showed good dielectric properties. The dielectric constant and dielectric loss tangent were less than 4.0 and 0.01, respectively. This work demonstrates that combining gelcasting and pressureless sintering is a practical approach for fabricating fused silica ceramics possessing good mechanical and dielectric performance through introducing ZrO 2 as reinforcement phase.