IRREVERSIBLE TRANSFORMATION OF HEXAGONAL BORON NITRIDE BY SHOCK COMPRESSION

Shock-wave compression measurements from 20 to 300 kbar are reported for hexagonal boron nitride, A phase transition occurs at 122 kbar and 230°C in good agreement with static data. The volume decrease is approximately 19% and the estimated slope of the phase line for the solid-solid transition is -3.6×10-2kbar °C-1. Crystallites of the dense phases recovered after shock compression above the transformation pressure were identified by x-ray diffraction as zinc blende cubic with traces of wurtzite.