Effects of P2O5 on sinterability, microstructures and properties of glass/alumina composites

We prepared the low-temperature fired glass/alumina composites and investigated the influence of P2O5 on the sinterability, microstructure, dielectric property, and mechanical strength. The result showed that although the nucleating agent P2O5 can promote the crystallization of CaO-B2O3-SiO2 (CBS) glass, excessive P2O5 have negative effects on the sintering behavior of composites. Because the density decreases gradually with increasing P2O5 addition, the dielectric and mechanical properties deteriorate dramatically. The densification mechanism via P2O5 modification is revealed further. Due to the crystallization effect of P2O5, the increase in viscosity impedes the flowability and wettability of liquid glass, which partly inhibits the liquid-phase sintering. 2 mol% P2O5-added CBS glass/alumina composite achieves densification at 900 °C (2.79 g/cm3) and exhibits good performances: low dielectric constant (5.84), low dielectric loss (1.17 × 10−3), and high flexural strength (166 MPa).