CORRELATION BETWEEN STRUCTURE AND HYDRIDING BEHAVIORS IN LAVES PHASES - ZR(MXCR1-X)2, M=FE, NI

In the MgZn2 hexagonal Laves phases, pseudo-binary compounds are prepared by changing M and Y in the formula: Zr(MxY1-x)2 M = Fe, Ni, Co, V and Y = Cr, Mn, V. Normally there is a linear decrease in the cell volume with increasing x. Replacement of Fe by Ni in the same proportion produces an anomalous change in the H-2 equilibrium pressure by reference to what can be predicted from the volume change. In fact, Ni substituted Laves Phases have the expected properties if the comparative parameter is no longer the cell volume but the tetrahedral H-2 host site volume. With this last criteria, both thermodynamic and kinetic parameters can be expressed by linear functions.