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.