A refractory silicon nitride joint, which contains beta-Si3N4 grains and gr
ain boundary amorphous phase in the joined layer, was developed with the ai
d of a ceramic adhesive based on the system Si3N4-Y2O3-SiO2-Al2O3. The simi
larity in chemistry and microstructure between the parent ceramic and the j
oint zone indicates that the joining mechanism is the same as that involved
in the sintering of Si3N4. The resultant joint exhibits a high bond streng
th of 550 MPa at 25 degrees C and retains a strength of 332 MPa at 1000 deg
rees C. Post-joining hot-isostatic pressing was applied to strengthen the j
oint, resulting in increased strengths of 668 MPa at room temperature and 4
64 MPa at 1000 degrees C.