A conjoint XRD–ND analysis of the crystal structures of austenitic and martensitic Ti0.64Zr0.36Ni hydrides

The crystal structures of the hydrides of austenitic and martensitic Ti0.64Zr0.36Ni alloy have been investigated by conjoint X-ray diffraction (XRD)–neutron diffraction (ND) analysis. Austenitic Ti0.64Zr0.36Ni alloy with cubic CsCl-type structure preserves its metal sublattice structure after deuteration. It forms a Ti0.64Zr0.36NiD1.5 deuteride with D-atoms occupying half of the octahedrally coordinated 3d sites. On the contrary, the monoclinic TiNi-type structure of martensitic Ti0.64Zr0.36Ni alloy is modified after deuterium absorption. At image and image, two deuterides coexist with orthorhombic CrB-type structure for the metal sublattice and compositions Ti0.64Zr0.36NiD (β-deuteride) and Ti0.64Zr0.36NiD2.6 (γ-deuteride). For the β-monodeuteride, deuterium atoms are tetrahedrally coordinated by (Ti,Zr) atoms. For the γ-deuteride, D-atoms fully occupy tetrahedrally coordinated (Ti,Zr)3Ni 8f sites and partially occupy pyramidal (Ti,Zr)3Ni2 4c sites. At higher pressures, deuterium solution occurs in the γ-phase with a partial occupancy of octahedrally coordinated (Ti,Zr)2Ni4 4a sites.