Microstructural investigations of Nb loaded with H were presented. The microstructure was examined by using positron annihilation spectroscopy, combined with X-ray diffraction and transmission electron microscopy. The behaviour of H-loaded bulk samples and thin films was compared. First, the microstructure of the virgin (H-free) specimens was characterized. Subsequently, the development of the microstructure during step-by-step electrochemical H charging was studied. The investigations were performed mainly in the low H concentration region (α-phase), where the Nb-H system represents a single-phase interstitial solid solution. In bulk samples it was found that new vacancy-like defects were introduced by H loading. Vacancies surrounded by H were detected also in the electron-irradiated bulk samples. Nanocrystalline thin films were produced by sputtering at room temperature. They exhibited a significant volume fraction of grain boundaries with open volume defects which trapped H.

Defect Studies of Hydrogen Loaded Nb - Bulk Metals and Thin Films. J.Cížek, I.Procházka, S.Daniš, O.Melikhova, M.Vlach, N.Zaludová, G.Brauer, W.Anwand, A.Mücklich, R.Gemma, E.Nikitin, R.Kirchheim, A.Pundt: Physica Status Solidi C, 2007, 4[10], 3485-8