A novel magnesium-vanadium hydride synthesized by a gigapascal-high-pressure technique

A magnesium-based vanadium-doped hydride was prepared in a high-pressure anvil cell by reacting a MgH2-25%V molar mixture at 8 GPa and 873 K. The new magnesium-vanadium hydride has a cubic F-centred substructure (a = 4.721 (1) Angstrom), with an additional superstructure, which could be described by a doubling of the cubic cell axis and a magnesium atom framework, including an ordered arrangement of both vanadium atoms and vacancies (a = 9.437(3) Angstrom, space group Fm (3) over barm (no. 225), Z = 4, V = 840.55,Angstrom(3)). The metal atom structure is related to the Ca7Ge type structure but the refined metal atom composition with vacancies on one of the magnesium sites corresponding to Mg6V nearly in line with EDX analysis. The thermal properties of the new compound were also studied by TPD analysis and TG-DTA. The onset of the hydrogen desorption for the new Mg6V hydride occurred at a 160 K lower temperature when compared to magnesium hydride at a heating rate of 10 K/min. (C) 2004 Elsevier B.V. All rights reserved.