RADIATION-INDUCED SCHOTTKY DEFECTS IN NACL

It has been found in nominally pure NaCl single-crystal samples that h ave been either gamma irradiated, plastically deformed or quenched int o liquid nitrogen from 700 degrees C, that an additional quenching wit h a short residence time at the quenching temperature,reveals the pres ence of dipolar defects by means of ionic thermocurrent (ITC) measurem ents. This procedure does not induce ITC signals in untreated samples. Since the occurrence of divacancies and divacancy clusters in plastic ally deformed or quenched samples is expected, it is pointed out that gamma irradiation may also form divacancies. The fact that all the ITC spectra of the samples treated in the above-indicated ways exhibit pe aks at similar temperatures also supports this view. The parallelism o bserved between the stored energy spectra of these samples and the evo lution of the ITC areas against the quenching temperature indicates th at the two phenomena are related. The occurrence of dipolar defects is consistent with a previous proposal: that the stored energy release i s due to the recombination of divacancies with alkali halide molecules .