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 pseudob inary LaNi5-xZnx alloys have been characterized by X-ray diffraction patter ns and hydrogen pressure-composition-temperature (PCT) diagrams at temperat ures ranging from 293 to 353 K. The P-C isotherms were used to determine th ermodynamic functions (enthalpy and entropy) for the hydrogen desorption pr ocess. Increasing Zn substitution causes the unit cell volume to increase a nd the plateau pressures to decrease. The maximum concentration of hydrogen in the tested La(Ni,Zn)(5) alloys slightly decreases with increasing Zn co ntent. (C) 2000 Published by Elsevier Science S.A. All rights reserved.