Structural study of ball-milled sodium alanate under high pressure

Ball-milled NaAlH 4 was studied up to 15 GPa in a diamond anvil cell (DAC) by X-ray diffraction using a synchrotron radiation source. Lattice parameters were determined from the X-ray diffraction data at various pressures up to 6.5 GPa. Intensity of the powder diffraction patterns decreased with increasing pressure. Amorphisation started at a pressure of ∼6.5 GPa and completed at 13.5 GPa. Reversible phase transformation from amorphous phase to the tetragonal phase was observed. A fit to the pressure–volume data equation of state was obtained using the Birch–Murnaghan equation of state and the bulk modulus was found to be 52.16 ± 0.9 GPa which is twice higher than the unmilled NaAlH 4.