POSITRON-ANNIHILATION IN THE QUENCHED AND ELECTRON-IRRADIATED NISB INTERMETALLIC COMPOUND

Samples of the near equiatomic NiSb compound were irradiated by 3 MeV electrons at 20 K or quenched from 1103 K and 1333 K and subsequently annealed isochronally. The behaviour of defects created by quench or i rradiation were studied by the positron annihilation technique. Only o ne recovery stage was found around 425 K for quenched specimens, but t wo distinct stages (100 K and 425 K) were observed after irradiation. The 425 K stage is ascribed to the migration of Ni vacancies giving di slocation loops. The recombination of mobile interstitials with vacanc ies after irradiation is assumed to occur between 100 K and 250 K. Dop pler broadening and lifetime variations of positrons as a function of the measuring temperature in these irradiation samples are discussed.