Neutron diffraction studies of the Zr 3P-D system

Abstract

Products obtained by absorption of different amounts of deuterium in Zr 3P have been investigated by X-ray and neutron diffraction methods. Crystal structure analyses were performed using the Rietveld profile refinement technique on the neutron data. In one sample, an interstitial solid solution of deuterium in Zr 3P was identified. Its composition corresponded to the formula Zr 3PD 0.15, with the Zr 3P sublattice essentially being unchanged as compared to that of the pure phosphide (Ti 3P-type, space group P 4 2 n ). A second more deuterium-rich sample was found to contain two phases in nearly equal amounts. One of them was a solid solution of deuterium in Zr 3P of the approximate composition Zr 3PD 0.78, while the other phase was found to be isostructural with the Zr 3PD 3−x phase (sublattice of the β-V 3S-type, space group P 4 2 nbc , x ≈ 0.1) reported in a previous study, its composition according to the structure refinement being close to Zr 3PD 2.60. In both cases, all deuterium atoms are surrounded by four near-neighbour zirconium atoms in more or less distorted tetrahedral arrangements. Assuming the action of local deuterium ordering, no D-Zr, D-P and D-D distances shorter than 1.9, 2.7 and 2.3 Å were observed.