In-situ observation of radiation-induced defects in ZrN under electron irradiation in HVEM

ZrN is a promising material for inert matrix fuel and transmutation targets in advanced nuclear applications. The nucleation-and-growth process of radiation-induced defects in zirconium nitride (ZrN) has been investigated in situ under electron irradiation by using a high voltage transmission electron microscope (HVEM) under the production of isolated Frenkel defects for both Zr and N atoms. Electron irradiation with 1250 keV at a constant electron flux of 4.4 x 1022m -2s-1 formed dislocation loops in a temperature range from 873 to 1273 K. The g & sdot;b analysis on the dislocation loops revealed that the Burgers vector of loops was parallel to (1 1 0) direction, indicating the formation of stoichiometric perfect-type dislocation loops. The areal density of loops increased with time to saturate above around 3000 s, and the saturation density decreased with increasing irradiation temperature. Analysis of the accumulation and saturation of dislocation loops using a rate equation showed that the formation of loops is controlled by diffusion and recombination of point defects with N vacancy formed by the non-stoichiometric composition (ZrN1-x). Further, the migration energy of interstitials for the rate-controlling species was evaluated to be 0.48 +/- 0.07 eV.