Hafnium Hydride and Hydrogenation of Thin Films

(Hafnium Hydride and Hydrogenation of Thin Films)

hafnium hydride is a non-toxic and safe compound that can be prepared by heating a metal salt with hafnium to a temperature sufficient to induce gel formation. The resulting gel can be deposited on glass or silicon substrates for use in electronic devices.

The hcp structure of sputtered thin films is reproducible qualitatively using NR and X-ray diffraction (XRD). These thin film hydrides have the same lattice constants as bulk hydrides.

Hydrogenation of sputtered Hf thin films by hydrogen pressure has been investigated. The hcp solid solution, formed on sputtering at high temperatures, consists of a large two-phase region separated by the d face-centred-cubic phase in which hydrogen occupies the interstitial tetrahedral sites. On further hydrogenation, a transformation takes place to the e face-centred tetragonal phase where the fcc lattice is compressed along the c axis.

The reversible and irreversible hydrogenation of sixteen intermetallics by a partial hydrogen pressure in the range 10+3 Pa to 0.8 Pa was studied. All the compounds except for one, in which a ternary hydride was formed, have an hcp structure.

During the hydrogenation process, the hcp structure is transformed to an fcc lattice, where the c axis is compressed and the d’ axis is extended. The volume of the host metal increases by about 16% on entering the fcc phase and an additional 2.8% within it19,20.

These results show that the reversible and irreversible hydrogenation can be easily studied in a controlled way. A single cycle of the hydrogenation can be used to determine the hcp and fcc plateau pressures as well as to identify the unloaded state of the hydride.

(Hafnium Hydride and Hydrogenation of Thin Films)