Changes in the defect structure of bulk material, caused by H loading, were investigated. The evolution of the microstructure, with increasing H concentration, was studied by means of X-ray diffraction, positron lifetime spectroscopy and slow positron implantation spectroscopy with measurements of Doppler broadening. Defect-free 3N-purity material, and samples which contained a large number of dislocations, were used. The samples were electrochemically loaded with H up to 0.06 [H/Nb] (the α-phase region). It was found that the defect density increased with H concentration. This implied that H-induced defects were created in the samples. A comparison of positron annihilation spectroscopic results with theoretical calculations revealed that vacancy-H complexes were introduced into the samples due to H loading. These were suggested to be vacancies which were surrounded by four H atoms.

Hydrogen-Induced Defects in Bulk Niobium. J.Cížek, I.Procházka, F.Bečvář, R.Kužel, M.Cieslar, G.Brauer, W.Anwand, R.Kirchheim, A.Pundt: Physical Review B, 2004, 69[22], 224106 (13pp)