Divacancies and the hydrogenation of Mg-Ti films with short range chemical order

Journal article (2010)
Department
Radiation, Radionuclides and Reactors (AS) (TU Delft)
Copyright: © 2010 The Author(s); American Institute of Physics
DOI: https://doi.org/doi:10.1063/1.3368698
Titanium Hydrogenation Magnesium Segregation Sorption Metal-insulator transition Sputter deposition Solid-state phase transformations Doppler broadening Electron spectra Metallic thin films Positron-surface impact Vacancies (crystal)
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Published Date

22-03-2010

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Source:

Applied Physics Letters, 96 (12), 2010

ISSN:

0003-6951

ISBN:

0003-6951

Source:

http://link.aip.org/link/APPLAB/v96/i12/p121902/s1

Faculty

Applied Sciences

Department

Radiation, Radionuclides and Reactors

Abstract

We obtained evidence for the partial chemical segregation of as-deposited and hydrogenated Mg1?yTiy films (0 ? y ? 0.30) into nanoscale Ti and Mg domains using positron Doppler-broadening. We exclusively monitor the hydrogenation of Mg domains, owing to the large difference in positron affinity for Mg and Ti. The electron momentum distribution broadens significantly upon transformation to the MgH2 phase over the whole compositional range. This reveals the similarity of the metal-insulator transition for rutile and fluorite MgH2. Positron lifetime studies show the presence of divacancies in the as-deposited and hydrogenated Mg-Ti metal films. In conjunction with the relatively large local lattice relaxations we deduce to be present in fluorite MgH2, these may be responsible for the fast hydrogen sorption kinetics in this MgH2 phase.

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