Microstructure and Strength of Si<sub>3</sub>N<sub>4</sub> Joints Bonded with Sialon-Oxynitride Glass

Abstract

Si5.4Al0.6O0.6N7.4(β-Sialon)/ Y1.75Si2.625Al1.0O7.5N1.25(oxynitride glass) composite solders with different ratio were designed using SiO2-Al2O3-AlN-Y2O3-Si3N4mixture powders to join Si3N4ceramic to itself. It was found that both solder composition and bonding temperature have strong influence on the microstructure and strength of the joints. As far as using a pure oxynitride glass solder was concerned, the thickness of the seam turned narrow with the increase of temperature, and the strength had a peak value at 1550 °C. When increasing the designed content of β-Sialon, serious composition separation occurred in the seam at low bonding temperatures, and the strength was also lower than as using pure oxynitride glass. Increasing bonding temperature, the strength of the joints was improved and reached the maximum value of near 80 MPa at 1600 °C for the designed 20%β-Sialon. In this instance, large amounts of fine elongated β-Sialon grains were uniformly distributed in the seam. However, for the 60%β-Sialon containing solder, some pores appeared in the seam and its strength was very low at bonding temperatures.