Liquid-phase bonding of silicon nitride ceramics using Y 2O 3–Al 2O 3–SiO 2–TiO 2 mixtures

Abstract

Hot-pressure sintered β-Si 3N 4 ceramic was bonded to itself using Y 2O 3–Al 2O 3–SiO 2–TiO 2 mixtures. Reactive behavior at interface between Si 3N 4 and Y 2O 3–Al 2O 3–SiO 2–TiO 2 mixtures during silicon nitride ceramic joining was studied by means of scanning electron microscopy (SEM), electron probe microanalyses (EPMA), X-ray diffraction (XRD) and auger electron spectroscopy (AES). The joint strength under different bonding conditions was measured by four-point bending tests. The results of EPMA, AES and XRD analyses show that the liquid glass solder reacts with silicon nitride at interface, forming the Si 3N 4/Y–Si–Al–Ti–O–N glass/TiN/Y–Si–Al–O glass gradient interface. From the results of four-point bending tests, it is known that with increase of bonding temperature and holding time, the joint strength increased reaching a peak, and then decreased. The maximum joint strength of 200 MPa measured by the four-point bending tests is obtained for silicon nitride bonded at 1823 K for 30 min.