A new ternary magnesium-titanium hydride Mg_7TiH_x with hydrogen desorption properties better than both binary magnesium and titanium hydrides

摘要

A magnesium based titanium doped hydride was prepared in a high-pressure anvil cell by reacting a mixture of MgH_2 and TiH_(1.9) at 8 GPa and 873 K. The metal structure has a Ca_7Ge type structure (a = 9.532(2) A, space group Fm3-bar m (no. 225), Z = 4, V = 866.06 A~3). The refined metal atom composition Mg_7Ti was almost in line with EDS analysis. This means that the new magnesium-titanium hydride has a structure that is more related to TiH_(1.9) than to MgH_2. The thermal properties of the new compound were also studied by TPD analysis. The new hydride, Mg_7TiH_x exhibits 5.5 mass percent (x approx= 12.7) and decomposes into Mg and TiH_(1.9) upon releasing 4.7 mass percent of hydrogen around 605 K, that is at a 130 and 220 K lower desorption temperature compared to MgH_2 and TiH_(1.9), respectively.