THE INFLUENCE OF SI AND GE ON THE HYDROGEN SORPTION PROPERTIES OF THE INTERMETALLIC COMPOUND ZRCR2

X-Ray powder diffraction studies of the Zr(Cr1-xTx)2 (T=Si, Ge) systems revealed that chromium can be replaced by silicon or germanium up to Zr(Cr0.75Si0.25)2 or Zr(Cr0.875Ge0.125)2 without changing the hexagonal MgZn2 structure type of ZrCr2. It was observed that all ternary alloys react readily with hydrogen to form hydrides containing 1.7-2.5 hydrogen atoms per formula unit under a hydrogen pressure of 0.1 MPa at room temperature. This is significantly lower than the value of 3.4 absorbed hydrogen atoms per formula unit found for the prototype binary compound ZrCr2 under the same conditions of pressure and temperature. Pressure-composition hydrogen desorption isotherms were determined over the temperature range 296-473 K and it was found that the replacement of chromium in ZrCr2 by silicon or germanium increases the hydrogen dissociation equilibrium pressure of ZrCr2. The hydrogen sorption properties of the systems described in this paper are compared with those of several related systems based on ZrCr2 and discussed briefly.