Structural mechanisms of rhombohedral BN transformations into diamond-like phases

Structural features and mechanisms of transformation of graphite-like rhombohedral boron nitride modification (rBN) into the diamond-like wurtzite (wBN) and zinc blende (zBN) types have been studied. The puckering mechanism of the rBN-->zBN transformation in shock waves was first proved structurally. It has been found that in static compression of CVD rBN (8 GPa, 20-2600 degrees C), transformations occur in the following sequence: rBN-->(S,T)-->I-g-->wBN-->I-d-->cBN, where (S,T) are structures deformed via basal shears or twinning, and I-g and I-d are intermediate graphite- and diamond-like structures, respectively. The structure of wBN formed from rBN has been shown to be much more disordered than that of wBN obtained from the BN hexagonal modification (hBN).