Radiation Hardening in Alkali-Halide Crystals

Abstract

Hardening by gamma irradiation was investigated in eleven alkali halides with the rocksalt structure. The linear dependence of the flow stress upon the one-half power of the F-center concentration, as previously observed in LiF and KCl, was also observed in these new substances. (The earlier experiments showed that the hardening is not actually caused by F cneters but by a defect resulting from F-center production.) The rate of hardening with concentration was found in all cases to be consistent with that to be expected for non-symmetrical defects. Comparisons were also made between the amount of hardening per defect and the lattice spaces available to certain specific defects. The only clear correlation was with a halogen atom in the interstitial space at coordinates 0, ¼, ¼ in the unit cell.