It was found that micro-cracks were formed in cubic nitride crystals, which had been grown by using a hot-pressing method, by annealing at temperatures above 673K. Analyses of the data which were obtained by means of transmission electron microscopy and diffraction showed that these micro-cracks did not extend on the most easily cleaved {110}-type planes, but extended on {111}-type planes. The electron energy-loss spectroscopic data indicated that the micro-cracks were formed via the condensation of excess N atoms onto {111}-type planes. It was noted that a micro-crack originated from a segment of 60º dislocation, and extended into the dilation side of the dislocation. That is, the habit plane of the micro-crack was not the glide-plane of the dislocation.

Formation of Microcracks in Cubic Boron Nitride. M.Aki, Y.Ohno, H.Kohno, S.Takeda: Philosophical Magazine A, 2000, 80[3], 747-58