Characterization of Al–Ti phases in cycled TiF3-enhanced Na2LiAlH6

TiF3-enhanced Na2LiAlH6 was investigated after dehydrogenation–hydrogenation cycles by synchrotron X-ray diffraction. There was no sign of Ti after ball-milling with TiF3, but two types of Al–Ti phases were observed in the cycled samples. In a sample after measuring five pressure–composition isotherms in the temperature range from 170 to 250 °C, a fcc phase with a = 3.987 Å was observed. This phase is considered to be Al3Ti with the L12 structure. Samples after one or four cycles at selected temperatures between 170 and 250 °C showed diffraction from another fcc phase with a ≈ 4.03 Å. This indicates formation of an Al1−yTiy solid-solution phase with y ≈ 0.15 similar to previously reported for cycled NaAlH4 with Ti additives.