Scandium hydride, also known as scandium–hydrogen alloy, is an

alloy An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...

made by combining

scandium Scandium is a chemical element; it has Symbol (chemistry), symbol Sc and atomic number 21. It is a silvery-white metallic d-block, d-block element. Historically, it has been classified as a rare-earth element, together with yttrium and the lantha ...

and

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

. Hydrogen acts as a hardening agent, preventing dislocations in the scandium atom

crystal lattice In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystal, crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that ...

from sliding past one another. Varying the amount of hydrogen controls qualities such as the

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by Pressing (metalworking), pressing or abrasion ...

of the resulting scandium hydride. Scandium hydride with increased hydrogen content can be made harder than scandium. It can be formed by progressive hydrogenation of

foil with hydrogen.Chemistry of d-block elements G. Singh (2007) In the narrow range of concentrations which make up scandium hydride, mixtures of hydrogen and scandium can form two different structures. At room temperature, the most stable form of scandium is the hexagonal close-packed (HCP) structure α-scandium. It is a fairly soft metallic material that can dissolve a moderate concentration of hydrogen, no more than 0.89 wt% at 22 °C. If scandium hydride contains more than 0.89% hydrogen at room temperature then it transforms into a face-centred cubic (FCC) structure, the δ-phase. It can dissolve considerably more hydrogen, as much as 4.29%, which reflects the upper hydrogen content of scandium hydride. Research indicates the existence of a third phase created under extreme conditions termed the η-phase. This phase can dissolve as much as 6.30% hydrogen. Concentration dependent activation-energies are observed for hydrogen diffusion in scandium metal.

References

{{Hydrides by group Metal hydrides Scandium compounds Rare earth alloys