THERMODYNAMICS AND STABILITY OF DISSOLVED HYDROGEN IN PD RICH BINARY PD(1-X)Z(X) AND TERNARY PD(1-X-Y)Z(X)Z(Y)' SOLID-SOLUTION ALLOYS

The relative chemical potential of the dissolved hydrogen (Delta mu(H) (O)) and the partial pair interaction free energies, g(P)(H)<---->(Z), and (g(H)(P)<---->(Z/Z'))(average) respectively, in Pd based Pd(1-x)Z (x)-H and Pd(1-x-y)Z(x)Z(y)'-H systems are correlated to the stability of the dissolved hydrogen in the octahedral interstitial sites by cla ssifying the Pd(1-x)Z(x) alloys based on the ''effective valence, n(s) '' of the substitutional metals. From the dependence of Delta mu(H)(O) on the lattice constant of the alloy, (a(0))(alloys) and of g(H)(P)<- --->((g(H)(P)<---->(Z/Z'))(average)) on the ionic diameter of the subs tituent metal, d(Z), ((d(Z/Z'))(average)) for systems Pd(1-x)Z(x)-H (P d(1-x-y)Z(x)Z(y)'-H), the exceptional behavior of the binary ''expande d'' alloys Pd(1-x)Z(x) (Z = Nb, Ta and Pt), the binary ''contracted'' Pd(1-x)Z(x) alloys (Z = Ti and Li) and the ternary ''contracted'' allo ys Pd0.903Er0.078Cu0.019 and Pd1-2xAgxNix towards hydrogen absorption is explained. (C) 1998 International Association for Hydrogen Energy.