High-Pressure Synthesis of Novel Hydrides and Intermetallic Compound in Al-X Systems (X=Sr, V, Hf)

Abstract

Al–based hydrides have been extensively investigated in order to their application for hydrogen storage. To explore new hydrides, the samples in Al–X–H systems (X = Sr, V, Hf) were synthesized at 873–1173 K for 2–8 h under 5 GPa with internal hydrogen source. Unidentified phases in XRD analysis were observed in samples with nominal composition of Al–50mol%SrH2, AlH3–60mol%VH2 and Al–50mol%HfH2. Judging from SEM–EDX analysis, the chemical composition of these phases were Al/Sr=1/1, Al/V=2/3 and Al/Hf=1/2. In Al–Sr system, hydrogen content was determined to be about 2.78mass% by fusion analysis. Corresponding chemical formula of the new hydride was estimated to be AlSrH3 with a perovskite–type crystal structure. Hydrogen desorption of 0.55 mass%H in the Al-60V sample was observed above about 400K by TG–TDS. The new compound, Al2V3H1.8~2.2 had a tetragonal structure. In Al–Hf system, the new compound had almost no hydrogen. Then, the chemical fomula of newly founf compound was estimated to be AlHf2 with a tetragonal structure.