Isotope effect in the superconducting palladium-hydrogen-deuterium system

Abstract

The dependence of critical temperature on hydrogen (deuterium) content in palladium hydride (deuteride) was measured on samples hydrogenized under equilibrium conditions with H(D) at high pressure. The superconductivity transitions can be observed for atomic ratios of hydrogen (deuterium) to palladium H(D)/Pd above 0.83 (0.77). The critical temperatures of deuteride are about 2.5K higher than those of hydride (at the same atomic ratios). The highest critical temperatures so far observed for the hydride and deuteride are 9.1K and 10.7K respectively. For both phases the effect of hydrostatic pressures is to decrease the critical temperature. The observed isotope effect does not support a metallic behaviour of hydrogen in palladium but is in reasonable agreement with Ganguly's model (see abstr. A6687 of 1974) for the superconductivity of palladium hydride or deuteride.