A neutron-diffraction study of the α phase in the palladium–gold–hydrogen and palladium–gold–deuterium systems

Abstract

It has been shown previously that both hydrogen and deuterium in β phase Pd–H and Pd–D are situated in the octahedral interstices of the f.c.c. palladium lattice, but attempts to determine the atomic positions in the α phase proved inconclusive, since only small amounts of gas are contained in this phase at room temperature. In order to locate the hydrogen atoms in the α phase by neutron diffraction the concentration must be increased. This can be accomplished by increasing die temperature and gas pressure. However, another method which avoids the use of high temperature and pressure was used in this investigation. This method is based on the observation that the addition of gold or silver to palladium results in increased hydrogen solubility in the α phase. Our neutron diffraction results on powdered α phase gold–palladium–hydrogen and gold–palladium–deuterium samples show that both hydrogen and deuterium are located in the octahedral positions of the f.c.c. metal lattice. It seems reasonable to assume that the same positions are occupied in the α phase of Pd–H.