The Phase Diagram of Mo-H Alloys under High Hydrogen Pressures

抄録

The phase diagram of the Mo–H system was determined by in situ X-ray diffraction using synchrotron radiation up to 1200^°C and the hydrogen pressure to p(H₂) = 5.3 GPa. Three phases were found to exist; a bcc phase (α) of low hydrogen concentrations at low hydrogen pressures, and two high-pressure phases, an hcp (ε) phase at lower temperatures and an fcc (γ) phase at higher temperatures, both having a nearly stoichiometeric composition of x = [H]/[Mo] ∼ 1. A gradual lattice contraction observed in the fcc phase indicates the formation of superabundant Mo-atom vacancies (vacancy-hydrogen clusters).