THERMODYNAMIC BEHAVIOR OF HYDROGEN IN PALLADIUM-GADOLINIUM SOLID-SOLUTION ALLOYS

The thermodynamic quantities for adsorption 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, ΔHHO, at infinite dilution becomes more exothermic with increasing Gd content. Whereas the standard relative partial entropy, ΔSHO, at infinite dilution decreases with Gd content. The results are discussed in terms of the quasi-chemical model by taking into the constant volume correction.