Bonding of silicon nitride ceramic composites with Y2O3–La2O3–Al2O3–SiO2 mixtures

Abstract

Silicon nitride ceramic composites were bonded using mixed Y2O3, La2O3, Al2O3, and SiO2 powers. The effect of bonding conditions on the joint strength was studied. The joint strength under different bonding conditions was measured by four-point bending tests. The interfacial microstructures were observed and analyzed by scanning electron microscopy, electron probe microanalysis (EPMA), and x-ray diffraction (XRD), respectively. The results of EPMA and XRD analyses showed that the liquid/glass solders reacted with silicon nitride at the interface, forming a Si3N4//Si2N2O/Y–La–Si–Al–O–N glass/Y–La–Si–Al–O glass gradient interface. From the results of the four-point bending tests, it is known that with an increase in bonding temperature and hold time, the joint strength first increased, reached a peak, and then decreased. LaYO3 precipitated from the joint glass can improve strength of the joint at both room and high temperatures.