2002 Volume 51 Issue 6 Pages 604-609
Mechanical properties of ceramics strongly depend on the machining condition. In the present study, surface defects and local strain, which was introduced by systematically machining the basal plane of sapphire, were characterized by cross-sectional transmission electron microscopy (XTEM) and convergent beam electron diffraction (CBED) technique. It was found that dislocations and strain were introduced from the surfaces for all specimens examined in this study. Depths of the introduced dislocation were measured by weak beam dark field (WBDF) method, and residual strain in the vicinity of the surfaces were precisely measured by CBED method using the probe size less than 10nm. The experimental CBED patterns were compared with the calculated patterns to quantitatively evaluate the lattice strain around the surfaces. Maximum penetration depths of the dislocations in the specimens ground with #500 diamond wheel, polished with 4-8μm and under 1μm diamond slurry were 1.7μm, 700nm and 250nm, respectively. In addition, twin defect was introduced in the specimen ground by #500 diamond to accommodated the large lattice strain during the machining. Residual local strain was found to remain at the depths of 1.0μm, 1.2μm and 300nm for the specimens ground with #500 diamond, polished with 4-8μm and under 1μm diamond slurry, respectively.