Irradiation-induced amorphization of titanite

摘要

Titanite (CaTiSiO5) is a widely occurring accessory mineral that contains ppm-level concentrations of U and Th. Radiation effects in titanite are important because this phase is commonly-used for U-Pb age dating of rock formations, and it is also the main crystalline constituent of certain glass-ceramic nuclear waste forms. Previous work suggested that titanite is highly susceptible to natural alpha-decay-induced amorphization, but ion irradiation experiments have so far been reported only at room temperature. In this work, the first temperature-dependent amorphization data for titanite are reported. High-purity single-crystal specimens from the Khan Mine, Namibia were characterized by analytical electron microscopy and powder XRD. Suitable specimens were then irradiated in-situ at the WEM Facility using 800 keV Kr ions at temperatures ranging from 30 to 1100 K. Conventional imaging and diffraction techniques were used to monitor the transformation to the amorphous state. Titanite was amorphized at a relatively low dose over the entire temperature range investigated. Limited crystallization of ion-beam-amorphized titanite was observed at temperatures above 1100 K.