A study of the crystallographic, magnetic and electronic properties of selected ZrM2-H systems

Dissolution of hydrogen into intermetallic compounds characteristically occurs at interstitial sites, causing little alteration to the base metal substructure but often bringing about substantial electronic and magnetic changes to the material. These hydrogen-induced alterations in the intermetallic hydrides are of interest both on a fundamental research level and in terms of technological applications; however, there exists no general theory as to how and why these alterations arise. The objective of this research is to elucidate to general effect of hydrogen on intermetallic compounds through the study of crystallographic, magnetic and electronic properties. An investigation has been carried out on the properties of three intermetallic compound - hydrogen systems of general formula ZrM₂, where M = V, Cr, Mn. All three compounds reversibly absorbed hydrogen with no change in crystal symmetry: powder diffraction studies showed that hydrogen was accommodated in interstitial sites of the existing metal sublattice via lattice expansion. The measurement of the magnetic properties of these systems was combined with the determination of conductivity and dielectric properties in order to describe the electronic e¤ects of hydrogen absorption. Despite the lack of signicant structural alteration in these systems, electron transfer between the metal sublattice and hydrogen may occur, as manifested in the appearance/disappearance of magnetic phenomena and the increase/decrease of electrical conductivity. Whilst the hydrogen addition in ZrM₂-H occurs simply via an expansion of the crystal structure, hydrogen does not act purely as null dilutant - there exist subtle electronic changes connected with the hydriding process as well