The diffusivity of hydrogen in palladium-based solid solutions

Abstract

An electrolytic method has been used to measure the temperature variation of the diffusivity of hydrogen in Pd-based substitutional solid solutions in the temperature range 270–350 K. The substitutional solutes were Fe, Co, Mn, Cr, and Ni. The kinetic data obtained for these systems, and previous data for systems containing the noble metals, transition metals of the First Long Period, and the Group V metals as substitutional solutes, have been analyzed in terms of equations derived by applying absolute rate theory to the cell model for ternary solid solutions. The analysis shows that the substitutional solute atoms create trapping sites for hydrogen atoms which are relatively shallow (0–4 kJ/mole) in comparison with sites created by the cold deformation of pure palladium (~ 20–40 kJ/mole). The noble metals create the shallowest trapping sites for hydrogen and the Group V metals the deepest.