Effect of BPO4-B2O3 Composite Additive on Crystallization and Sintering of Silica Ceramics

BPO4-B2O3 composite additive enhanced silica ceramics were successfully prepared by solid phase sintering. The effects of BPO4-B2O3 addition and sintering temperature on the microstructure and phase composition and mechanical properties of silica ceramics were analysed by scanning electron microscopy and X-ray diffraction techniques. The results showed that at 1200°-1400°C, BPO4-B2O3 composite additive formed a glass phase in the sample, filled the pores, and improved the sintering densification of the sample. In addition, the addition of 9 wt% BPO4-B2O3 successfully inhibited the crystallization of fused silica, which significantly improved the mechanical strength of silica ceramics. After sintering at 1200°C for 3 h, the apparent porosity of silica ceramics with 9 wt% BPO4-B2O3 was only 1.33%, and the cold modulus of rupture reached a maximum of 60.99 MPa, which was about 35 times that of pure silica ceramics. It is shown that adding BPO4-B2O3 composite additive provides a feasible method for preparing silica ceramics with good mechanical properties.