Thermodynamic Behavior of Hydrogen in Palladium‐Gadolinium Solid Solution Alloys

Publisher Website
Google Scholar
Abstract
The thermodynamic quantities for absorption of hydrogen by disordered Pd — Gd solid solution alloys containing up to 8.0 at.% Gd have been determined at temperatures between 273 and 473 K and hydrogen pressures up to 100 Torr by measuring the pressure‐composition isotherms. The standard relative partial molar enthalpy of solution of hydrogen, ΔH0H, at infinite dilution becomes more exothermic with increasing Gd content. Whereas the standard relative partial entropy, ΔS0H, at infinite dilution decreases with Gd content; this implies that the octahedral interstices are excluded for hydrogen occupation by Gd neighbors. Substitution of Gd in the Pd lattice decreases the apparent H‐H attractive interaction and for the Pd‐4.5 and 6.0 at.% Gd alloys the H‐H interaction becomes repulsive over a certain range of H contents. The results are discussed in terms of the quasi‐chemical model by taking into the constant volume correction. The stability of P‐hydride phase increases with Gd content, and the extent of the phase boundary, i.e., the hydrogen solvus composition at a given temperature, is more favourable by Pd alloying with Gd.

This publication has 51 references indexed in Scilit: