Interaction of hydrogen and deuterium with intrinsic atomic defects in high-purity electron-irradiated nickel

Abstract

High-purity nickel was irradiated with 2 MeV electrons at temperatures below 80 K to a dose of 1 × 10²³ e^?/m² in the as-prepared state and after charging with H or D. By means of magnetic after-effect measurements relaxations of anisotropic radiation-induced defects and of defect-hydrogen complexes were investigated in the temperature range between 4.2 and 500 K. The isochronal annealing behaviour of these relaxations and the isochronal recovery of the residual resistivity was measured simultaneously on the same specimens. At temperatures below the hydrogen mobility (< 160 K) in charged irradiated specimens relaxation maxima are observed at 45, 100, 115 and 140 K which show no isotope shift for H and D charging. The maxima below 160 K are explained by defect-hydrogen complexes, where radiation-induced defects reorient around immobile hydrogen atoms. Above 160 K, where hydrogen atoms get mobile, in charged irradiated specimens a broad relaxation maximum appears at 170 K which shows an inverse isotope shift for H and D charging. This 170 K maximum anneals in Stage III. A hydrogen diffusion maximum observed in charged specimens at 215 K prior to irradiation is missing after electron irradiation. The 170 K relaxation is explained by defect-hydrogen complexes, where hydrogen atoms reorient around immobile radiation-induced defects while the long-range hydrogen diffusion is suppressed by these defects. In such relaxation measurements hydrogen and deuterium atoms are used as a “probe” to investigate radiation-induced defects.