Influence of γ-Irradiation on Some Properties of NaCl:Eu++ Crystals (III). Strengthening Effects

Mechanical strength of europium-doped NaCl crystals was studied as function of dopant concentration and dopant dispersion state as well. It has been found that the yield stress of the solution-treated samples is determined by the Snoek-type reorientation of dipoles in the stress field of moving dislocations. For as received samples the precipitation strengthening mechanisms are postulated. Irrespective of the dispersion state of europium, the strength of all NaCl:Eu⁺⁺ crystals can be remarkably changed by the room temperature irradiation. Although the yield stress increments can be explained in frames of the precipitation-strengthening mechanisms, the radiation-induced processes depend on the primary disprsion e state of the dopant. As far as the solution-treated samples the clustering of I.V. dipoles is of main importance, it is necessary to assume that dispersion of precipitates is required to achieve the strength of irradiated as received samples.