Extrusion of quartz on ion bombardment: Further evidence for radiation-induced stress relaxation of the silica network

It is shown that although crystal quartz shows a highly aeolotropic uniaxial radiation expansion when it is disordered with energetic neutrons, plates of crystal quartz oriented on either principal axis exhibit a perpendicular expansion equivalent to the total volume expansion without developing porosity when subjected to bombardment with protons, deuterons, or helium ions having ranges about a micron. Thus a plastic flow must occur during ion bombardment. A mechanism for these courses of transformation is given: that the crystal structure breaks up into a mosaic of units elongated parallel to the optic axis in a vitreous matrix. The elongated units could account for the relative behavior of various aeolotropic properties, and the vitreous matrix could facilitate plastic flow.