Properties of amorphousZr3RhHxprepared from glassy and crystalline alloys

The electronic, magnetic, and thermal properties have been measured on the amorphous hydride phases prepared from originally glassy or crystalline ${\mathrm{Zr}}_3$Rh alloys. The a-${\mathrm{Zr}}_3$ ${\mathrm{RhH}}_{\mathrm{x}}$ samples with x≤5.5 were studied by x-ray diffraction, proton nuclear magnetic resonance, magnetic susceptibility, low-temperature heat capacity, differential scanning calorimetry, and inelastic neutron scattering. All hydride samples are amorphous with similar properties which are shown to be independent of the structure for the initial alloy. Namely, the solid-state reaction of hydrogen with crystalline c-${\mathrm{Zr}}_3$Rh appeared to produce an equivalent amorphous phase to hydrogenated glassy alloys. The changes in the electronic and magnetic properties upon hydrogenation imply a systematic decrease in the Fermi-level density of states in a-${\mathrm{Zr}}_3$ ${\mathrm{RhH}}_{\mathrm{x}}$ as the hydrogen content x increases. The thermal stabilities of the amorphous hydrides (with respect to the irreversible formation of crystalline ${\mathrm{ZrH}}_{\mathrm{x}}$ phases) also decrease with increasing hydrogen stoichiometry. Whereas the hydrogen atoms predominantly occupy tetrahedral interstitial sites coordinated with zirconium atoms, there is strong circumstantial evidence for occupancies of different and less stable sites for compositions with higher hydrogen content.