Electronic influences in the diffusion of hydrogen in the alloy series of palladium

The mobility of tritium in Pd-alloys with Ag, V and Ni has been investigated by time-lag measurements, where the β-radiation of the tritium decay was taken as measuring signal; this method allows the determination of internal concentration shifts without disturbance by inhibiting effects of interface transfer. It has been found, that small additions of the alloying components do not change the activation energy of tritium diffusion; higher concentrations of Ag and V, however, lead to steep rises of the activation energy, whereas the isoelectronic Ni as alloying partner does not influence the activation energy within the limits of experimental error. For interpretation of the results the activation energy of diffusion is divided into a basic contribution of the Pd host lattice and an additional electronic term. This term is closely connected with the VEC, and can be calculated from the screening potential of the impurity atoms. The basic part of the activation energy can approximately be identified with the energy of elastic strain of the Pd lattice brought about by the diffusion jump. (orig.)