X-ray diffraction studies of titanium and zirconium doped NaAlH4: elucidation of doping induced structural changes and their relationship to enhanced hydrogen storage properties

• Published in: Journal of alloys and compounds Vol. 337; no. 1-2; pp. L8 - L11
• Main Authors: Sun, Dalin, Kiyobayashi, Tetsu, Takeshita, Hiroyuki T., Kuriyama, Nobuhiro, Jensen, Craig M.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 02.05.2002; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Hydrogen absorbing materials; Inorganic compounds; Metal hydrides; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Vacancy formation; X-ray diffraction; X-ray diffraction; Metal hydrides; Hydrogen absorbing materials; Vacancy formation; Aluminium hydrides; Hydrogen storage; Inorganic compounds; Phase transformations; Ternary compounds; Doping; XRD; Lattice parameters; Titanium additions; Zirconium additions; Ion substitution; Valence; Impurities; Sodium hydrides; Impurity states; Defect formation
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/S0925-8388(01)01955-7

X-ray diffraction patterns of NaAlH4 doped with up to 10 mol.% of either titanium or zirconium do not contain Bragg peaks for the bulk metals or their aluminum alloys. Instead the hydride lattice parameters a and c undergo significant contraction upon 2 mol.% doping and then expand as the doping level increases from 2 to 5 mol.%. These results are explained by a model that entails substitution of sodium cations by variable valence transition metal cations and the creation of Na+ vacancies in the bulk hydride lattice.