Orientation and growth of grains in copper-activated hot-pressed hexagonal boron nitride

Hexagonal boron nitride powder was hot pressed in an environment of metallic copper. When compared with a copper-free system, the sintered body exposed to the copper was composed of substantially thicker grains having an unusual arrangement, consisting of preferred alignment of (0001) basal planes parallel to the pressure axis. The character of the orientation of the boron nitride grains substantially influenced the mechanical strength of the ceramics. The difference in the orientation of the grains is explained by the interaction between copper atoms and boron nitride crystals selectively occurring on the (0001) basal planes of the latter.