| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1619560 | Journal of Alloys and Compounds | 2011 | 5 Pages |
Positron depth-profiling was applied to monitor the effects of hydrogenation on Mg1−yTiy thin films. S–W diagrams and VEPFIT analysis of the depth-profiles demonstrated the homogeneity of most metal and metal hydride films. In contrast, Mg0.90Ti0.10Hx films consisted of a double layer, with a thin unloaded Mg0.90Ti0.10 or Mg–Ti–Pd alloy layer on top of a hydrogenated bottom layer. The metal-to-metal-hydride transformation of Mg domains in the nanoscale phase-segregated Mg–Ti films was monitored exclusively, enabled by the large difference in positron affinity for Mg and Ti. The changes in the Doppler broadening parameters revealed that the metal–insulator transition for fluorite MgH2 is similar to that for rutile MgH2. Positron lifetime spectroscopy showed the presence of di-vacancies in the metal sub-lattice of as-deposited and hydrogenated Mg–Ti metal films, which may induce the fast hydrogen sorption kinetics of the fluorite MgH2 phase.
Research highlights▶ Positron depth-profiling revealed a double layer in hydrogenated Mg–Ti–H films. ▶ Positrons probe Mg(H2) regions in nanoscale segregated Mg–Ti(–H) films exclusively. ▶ The metal-insulator transition for fluorite MgH2 is similar to that for rutile MgH2. ▶ Divacancies in Mg–Ti and Mg–Ti–H films were found by positron lifetime spectroscopy. ▶ Positron annihilation and X-ray scattering provided highly complementary results.
