X-ray and positron annihilation studies of radiation damage in natural zircons

Abstract

Photographic measurements, using a precession camera, were made of the diffuse X-ray scattering from zircons (ZrSiO₄) subjected to natural radiation damage. The diffuse scattering was concentrated near the zircon reciprocal-lattice positions only and the intensity contours could approximately be described by spheres. However in fairly severely damaged samples there were significant deviations from circularity of the diffuse intensity contours in the (hk0)reciprocal-lattice planes but not in the (0kl) planes. Positron annihilation lifetime spectra were obtained for lightly damaged zircon and were satisfactorily fitted by three lifetime components. Annealing and ionizing radiation produced changes in the intensities of the longer-lived components of the positron lifetime spectra. These changes appeared mainly to derive from bleaching and re-coloring of electron- or trapped hole-centers associated with displaced ions rather than those associated with impurity ions.