Deuterium solubility and electrical resistance of palladium-rhodium alloys

The deuterium solubility and the corresponding change in electrical resistance 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 pressure deuterium solubilities and increase in plateau pressures with increasing Rh content have been observed. The decrease in lattice size with increasing Rh content seemed responsible for it. The miscibility gap decreased with increasing Rh content. Higher deuterium solubility was attained for lower Rh content alloy. The studied systems showed remarkable p-c hysteresis. The 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 αmax resistance values are gradually decreased with increasing Rh content and increased with increasing temperature. The initiation of β deuteride creates pronounced lattice deformation and R/R0 values increased sharply. For a higher Rh content alloy, the increase in R/R0 values during β hydride initiation is higher, probably for its smaller lattice size. At higher temperatures, a lowering of resistance occurred when the system entered from a coherent state to an incoherent state. In the main plateau region, the change in R/R0 showed small values. From D/M content of about 0.55, a pronounced lowering of resistance, was observed, probably due to approaching of the β 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 system. Larger lattice expansion and the creation of higher lattice deformation in the β phase region due to a higher amount of deuterium absorption seemed responsible for it. The R/R0-c behavior showed a good similarity with that of their hydrogen system found by the same method, but dissimilar to that reported by the electrochemical method.