Deuterium solubility and electrical resistance of palladium-rhodium alloys

The deuterium solubility and the corresponding change in electrical resista nce of Pd-5.0 and -10.0 at.% Rh alloys have been investigated at different temperatures by a gas phase method. In these studies, a decrease in low pre ssure deuterium solubilities and increase in plateau pressures with increas ing Rh content have been observed. The decrease in lattice size with increa sing Rh content seemed responsible for it. The miscibility gap decreased wi th increasing Rh content. Higher deuterium solubility was attained for lowe r Rh content alloy. The studied systems showed remarkable p-c hysteresis. T he loss in energy due to hysteresis for the Pd-10.0 at.% Rh-D system showed lower values than that of the Pd-5.0 at.% Rh-D system. The alpha(max) resi stance values are gradually decreased with increasing Rh content and increa sed with increasing temperature. The initiation of beta deuteride creates p ronounced lattice deformation and R/R-0 values increased sharply. For a hig her Rh content alloy, the increase in R/R-0 values during beta hydride init iation is higher, probably for its smaller lattice size. At higher temperat ures, a lowering of resistance occurred when the system entered from a cohe rent state to an incoherent state. In the main plateau region, the change i n R/R-0 showed small values. From D/M content of about 0.55, a pronounced l owering of resistance, was observed, probably due to approaching of the bet a phase structure to a NaCl type lattice. Remarkable resistance hysteresis was observed at the studied temperatures. For the Pd-5.0 at.% Rh-D system a larger resistance hysteresis appeared than that of the Pd-10.0 at.% Rh-D s ystem. Larger lattice expansion and the creation of higher lattice deformat ion in the beta phase region due to a higher amount of deuterium absorption seemed responsible for it. The R/R-0-c behavior showed a good similarity w ith that of their hydrogen system found by the same method, but dissimilar to that reported by the electrochemical method. (C) 2000 International Asso ciation for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.