Joining of ceramics using oxide and oxynitride glasses in the Y-sialon system

Glasses in the Y-SiAlO and Y-SiAlON systems, of standard cation composition (28: Y, 56:Si, 16:Al) have been investigated as potential adhesive materials for silicon nitride-based ceramics. Glass transition and crystallisation temperatures are reported. Hardness and density have also been measured. These glass materials have been used to bond hot-pressed and sintered β-sialon ceramics containing an inter-granular glass composition similar to that of the adhesive material. Joints were formed via two processes: (1) hot-pressing at temperatures from 1130°C to 1600°C for 1 h at a pressure of 5 MPa using the Y-sialon glass; and (2) pressureless sintering at 1600°C for 1 h, using both the Y-sialon and Y-sialo glasses. At a temperature of 1600°C, SEM analysis illustrates that both processes yield visibly good joints. Hardness measurements indicate that there is no degradation in value between the parent ceramic and the bonded region. Joining was dominated by the flow of glass across the ceramic interfaces, dissolution of the individual grains within the glass and reprecipitation of the Si₃N₄ across the interface reinforcing the joint.