HYDRIDING PROPERTIES OF CE(MN, AL)(2) AND CE(FE, AL)(2) INTERMETALLICCOMPOUNDS

A major breaktrough in the developement of metal hydrides for hydrogen storage will require inexpensive intermetallic compounds that absorb large quantities of hydrogen at near ambient conditions (atmospheric p ressure and room temperature). Unfortunately, in the last ten years th ere has been relatively little progress in this field. We investigated intermetallic compounds Ce(T1-yAly)(2) with T=Mn, Fe in the range 0.5 less than or equal to y<1.0. Mn, Fe and Al are inexpensive and Ce cou ld be replaced by the low cost mischmetal (MM). The intermetallic comp ounds Ce(T, Al)(2) form the C14 and C15 Laves phases and they absorb h ydrogen. A fraction of the totally absorbed hydrogen of about 2.5 H/(f ormula unit) forms a stable hydride (beta-phase) at low pressures (<10 mbar). An additional H/(f.u.) is absorbed and reversibly desorbed at hydrogen pressures >10 mbar. The alloys and their hydriding characteri stics were analyzed by means of X-ray diffraction and pressure-concent ration isotherms. The two different absorption behaviours are correlat ed to the occupation of 96g-positions with different surrounding atomi c constitutions. (C) 1997 Elsevier Science S.A.