Irreversible Transformation of Hexagonal Boron Nitride by Shock Compression

Abstract

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.