Nano-scale glass formation in pyrochlore by heavy ion irradiation

Irradiation-induced amorphization in a pyrochlore (Na,Ca)2Nb2O6(F,OH,O) and a microlite (Na,Ca)2 Ta2O6(F,OH,O) have been studied over a temperature range of 300–873 K by in situ transmission electron microscope (TEM) using 1 MeV Kr+ and 400 keV Xe+ with a dose rate of 8.5×1011 ions/cm2/s. Isolated nanometer-sized domains of glass were observed by high-resolution electron microscopy in the Xe+-irradiated samples. The density of these domains has a ‘one-to-one’ correlation to the ion density, consistent with the amorphous domains having formed directly within the displacement cascade. The effect of temperature on the amorphization dose was modeled based on a cascade quenching mechanism. A two-stage function was observed in the temperature dependence of amorphization dose for both the pyrochlore and microlite.