Hydrogen-induced defects in niobium studied by positron annihilation spectroscopy

Changes of the defect structure of niobium induced by hydrogen loading are presented in this work. The evolution of the microstructure with increasing hydrogen concentration was studied by X-ray diffraction and two complementary techniques of positron annihilation spectroscopy (PAS). A comparison of PAS results with theoretical calculations revealed that complexes consisting of a vacancy, surrounded likely by four hydrogen atoms, were introduced into the samples due to hydrogen loading.