Evidence of ⟨a + c⟩ dislocations in synthetic quartz single crystals compressed along the c axis

Abstract

When compressed along the c axis, quartz single crystals can accomodate deformation either by pure climb of ⟨c⟩ and ⟨a⟩ dislocations or by glide of ⟨c + a⟩ dislocations in rhombohedral and pyramidal planes {10[-1]1}, {11[-2]2} and {10[-1]1}. Detailled TEM investigations on samples deformed at high temperature clearly show ⟨c + a⟩ dislocations lying in {10[-1]1} and {11[-2]2} planes. The various possible mechanisms (climb versus glide) for this orientation are discussed.