Concentration profile of hydrogen near the surface of niobium

The results show that experiments on samples of niobium-hydrogen, or similar materials hydrided in the manner described must take into account the possible existence of an appreciable hydrogen concentration gradient towards the surface. Experiments which are especially affected by this result are x-ray diffraction experiments and other techniques which probe the near-surface regions of a sample. In x-ray measurements the sampling depth is in the range of the hydrogen-depleted and oxygen-enriched zone, and this factor may very well lead to incorrect conclusions. This parameter may be the reason for the finding of Zabel, Schoenfeld, and Moss that a approx. 1 μm thick hydrogen-depleted layer existed on the surface of a crystal which was essentially in the α'-phase. 14 references, 1 figure