Crystal structure of the high-pressure modification of NdTaO4

Both X-ray and neutron diffraction Rietveld analyses show that the as-cast ZrCr0.7Ni1.3 alloy crystallises with the C15-type Laves phase type structure, with the presence of >30 wt.% Zr7Ni10 and a few weight percent chromium. After annealing at 1373 K, we observed the disappearance of chromium metal and a reduction by more than half of Zr7Ni10. P–C–T measurements performed on the as-cast material show an absorption capacity of about 0.9 H/AB2 at 323 K and under P=10 bar. In-situ neutron diffraction experiments performed at 323 K under deuterium gas pressure reveal that, after full hydrogenation of the sample, the Zr7Ni10 phase transforms into an amorphous phase, but recrystallises under vacuum when the temperature is raised above 373 K.