Hydrogenation equilibria characteristics of LaNi5-xZnx intermetallics

A series of metal hydride alloys were prepared based on the LaNi5 formula, by substituting 0, 5, 10, 15 and 20 at.% of Zn for Ni. The obtained pseudobinary LaNi5-xZnx alloys have been characterized by X-ray diffraction patterns and hydrogen pressure-composition-temperature (PCT) diagrams at temperatures ranging from 293 to 353 K. The P-C isotherms were used to determine thermodynamic functions (enthalpy and entropy) for the hydrogen desorption process. Increasing Zn substitution causes the unit cell volume to increase and the plateau pressures to decrease. The maximum concentration of hydrogen in the tested La(Ni,Zn)(5) alloys slightly decreases with increasing Zn content. (C) 2000 Published by Elsevier Science S.A. All rights reserved.