THERMAL PHASE-STABILITY OF RHOMBOHEDRAL BORON-NITRIDE

Thermal phase stability of rhombohedral baron nitride has been studied between 0 and 8 GPa from 300 to 2700 K. Analysis of the data obtained points to the decisive role of kinetic factors in the rBN phase trans formations, the structure and dispersity of the samples under study be ing of great importance. rBN phase transformations in the cBN thermody namic stability region of the equilibrium p,T phase diagram for boron nitride occur according to Ostwald stepwise principle by the rBN --> h BN --> (wBN) --> cBN scheme.