Solubility of Hydrogen in Palladium-Yttrium-Silver Alloys

TLDR: In this article, the authors compared the absorption properties of Pd95-xYxAg5 solid solution alloys with up to 6.3 at with those of binary alloys.

Abstract: Thermodynamic quantities for absorption of hydrogen by Pd95–xYxAg5 solid solution alloys with up to x = 6.3 at.% Y have been determined from measurements of pressure-composition isotherms at temperatures between 273 K and 473 K and hydrogen pressures up to 1000 Torr. The hydrogen absorption characteristics have been compared with those of the previously reported Pd–Ag and Pd–Y binary alloys. The relative partial molar enthalpy, ΔHH0, at infinite dilution of hydrogen in Pd95–xYxAg5 alloys increases in exothermicity with increasing Y content from that of Pd–5.0 at.% Ag, almost parallel to that in Pd–Y binary alloys. The relative partial molar entropy, ΔSH0, at infinite dilution in the ternary alloys decreases with Y content from that of Pd–5.0 at.% Ag alloy. The hydrogen solubility behavior at low hydrogen concentration in the Pd–Y–Ag alloys under a “constant volume” condition can be described as due to mainly the strong H–Y attractive pair interaction in the Pd host lattice. The stability of β-hydride and hydrogen concentration at αmax phase boundary increase following alloying with Y from that of Pd–5.0 at.% Ag alloy, respectively, and the changes in the properties with Y content are similar to that in Pd–Y binary alloys.