We obtained evidence for the partial chemical segregation of as-deposited and hydrogenated films 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 phase over the whole compositional range. This reveals the similarity of the metal-insulator transition for rutile and fluorite . 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 , these may be responsible for the fast hydrogen sorption kinetics in this phase.
Divacancies and the hydrogenation of Mg-Ti films with short range chemical order
H. Leegwater, H. Schut, W. Egger, A. Baldi, B. Dam, S. W. H. Eijt; Divacancies and the hydrogenation of Mg-Ti films with short range chemical order. Appl. Phys. Lett. 22 March 2010; 96 (12): 121902. https://doi.org/10.1063/1.3368698
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