Migration of hydrogen isotopes in Pd and Pd-Fe dilute alloys at ion temperatures

The migration of hydrogen isotopes in pure Pd and Pd-Fe dilute alloys were studied by measuring the electrical resistance at low temperatures. The hyd rogen isotopes were charged by heating in a high pressure gas atmosphere of the hydrogen isotopes, or by electrolysis in single crystal plates or poly crystalline wires. The disordered hydrogen isotopes produced by the quenchi ng, migrate to order during annealing. The electrical resistance of the spe cimen increases due to the ordering and decreases due to the disordering of the hydrogen isotopes. From Various isothermal annealing curves for the sa me specimen, each relaxation time for the resistance increase is determined for various temperatures. The migration energies of hydrogen isotopes are obtained from the above relaxation times for various concentrations of hydr ogen isotopes. The obtained values in pure Pd are nearly the same for singl e crystal specimen and polycrystalline specimen. The values also do not dep end on the hydrogen charging method and also on the hydrogen concentration. These values for hydrogen and deuterium atoms are smaller than those value s at high temperatures, respectively. This is caused by the tunnel effects of migration which become important at low temperatures for light atoms. Th e ratio of the diffusion coefficients, D-H/D-D, decreases with decreasing t emperature. The migration energies of hydrogen isotopes in Pd-Fe dilute all oys are larger than the values for pure Pd. The behavior of the D-H/D-D rat io of the alloys is also the same for that of pure Pd.