Bonding silicon nitride using Y2O3-Al2O3-SiO2 adhesive

Pressureless sintered silicon nitride ceramics were joined using mixed Y2O3 , Al2O3, SiO2 and Si3N4 powers. Joining was carried out at 1450 and 1600 de grees C for 30 min, under an applied pressure of 5 MPa. The result of EPMA in the cross-section of the joined region indicated that some elements of a dhesive (Y, Al) diffused into Si3N4 to form a diffusion layer at lower temp erature (1450 degrees C), but elements of Y and Al were distributed uniform ly all over the cross-section of the joined samples at higher temperature ( 1600 degrees C). From the results of 3-point bending measurement, an averag e strength of 400 MPa was obtained for the samples bonded at 1600 degrees C , which was approximately 57% of that of unbonded ceramics. (C) 1999 Elsevi er Science Ltd and Techna S.r.l. All rights reserved.