The hydrogenation of Dy5Pd2 followed by in situ methods

• Published in: Journal of solid state chemistry Vol. 187; pp. 244 - 248
• Main Authors: Kohlmann, H., Talik, E., Hansen, T.C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.03.2012; Elsevier
• Subjects: Atomic structure; Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Differential scanning calorimetry; Diffraction; Dysprosium; Dysprosium hydride; Exact sciences and technology; Hydrogen storage; Hydrogenation; In situ techniques; Metal hydrides; Neutron diffraction and scattering; Occupation; Palladium; Physics; Single-crystal and powder diffraction; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Theory of crystal structure, crystal symmetry; calculations and modeling; Thermal analysis; Metal hydrides; Thermal analysis; Hydrogenation; In situ techniques; Dysprosium hydride; Deuterium; Differential scanning calorimetry; Temperature dependence; Pressure effects; Intermetallic compounds; Neutron diffraction; Hydrides; Palladium; XRD; Dysprosium; Heat treatments; Nonstoichiometry; Structural models; Powder pattern; Experimental design; Rate equation; Crystal structure
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2012.01.029

The hydrogenation behavior of the intermetallic compound Dy5Pd2 was investigated by means of ex situ X-ray powder diffraction, in situ neutron powder diffraction and in situ differential scanning calorimetry. The structural model of Dy5Pd2 with a palladium atom at the 32(e) position x, x, x (x≈0.22, 7/8 occupation) and a dysprosium atom at almost the same location (x≈0.18, 1/8 occupation) is confirmed. Upon heating the latter approaches x(Pd) and at T=399K both positional parameters are indistinguishable. Dy5Pd2 does not incorporate hydrogen (deuterium) into its crystal structure, however, starting at T=495K reacts with hydrogen to non stoichiometric dysprosium dideuteride, DyD2+x, following a parabolic rate law. In situ differential scanning calorimetry at various hydrogen pressures up to 2.5MPa shows strongly exothermic signals, whose temperature onset depend on the gas pressure, corresponding to the formation of a mainly ionic hydride (DyH2+x). The hydrogenation of Dy5Pd2 is being followed by in situ neutron diffraction. [Display omitted] ► Dy5Pd2 does not form a ternary hydride upon hydrogenation. ► Dy5Pd2 decomposes to binary hydrides of dysprosium and palladium. ► At T≥399K Dy3 and Pd in the crystal structure of Dy5Pd2 share the same position. ► The formation of DyD2+x at T=495K and p(D2)=2.5MPa follows a parabolic rate law.