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
2010 Applied Physics Letters  
We obtained evidence for the partial chemical segregation of as-deposited and hydrogenated Mg 1−y Ti y films ͑0 Յ y Յ 0.30͒ 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 MgH 2 phase over the whole compositional range. This reveals the similarity of the metal-insulator
more » ... e metal-insulator transition for rutile and fluorite MgH 2 . 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 MgH 2 , these may be responsible for the fast hydrogen sorption kinetics in this MgH 2 phase.
doi:10.1063/1.3368698 fatcat:ho7j4t44ljd7zmjkg4ujki4afi