Hydrogen acts as a hardening agent, preventing dislocations in the scandium atom crystal lattice from sliding past one another.
Varying the amount of hydrogen controls qualities such as the hardness of the resulting scandium hydride.
At room temperature, the most stable form of scandium is the hexagonal close-packed (HCP) structure α-scandium.
[2] 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.