The preparation of Zr-deuteride and phase stability studies of the Zr-D system

Deuteride phases in the zirconium-deuterium system in the temperature range 25-286$\celsius$ have been studied in-situ by high resolution neutron diffraction. The study primarily focused on observations of $\delta \rightarrow \gamma$ transformation at 180$\celsius$, and the peritectoid reaction $\alpha + \delta \leftrightarrow \gamma$ at 255$\celsius$ in commercial grade Zr powder that was deuterated to a deuterium/Zr ratio of one to one. A detailed description of the zirconium deuteride preparation route by high temperature gas loading is also described. The lattice parameters of $\alpha$-Zr, $\delta$-ZrD$_x$ and $\epsilon$-ZrD$_x$ were determined by whole pattern crystal structure analysis, using Rietveld and Pawley refinements, and are in good agreement with values reported in the literature. The controversial $\gamma$-hydride phase was observed both in-situ and ex-situ in deuterated Zr powder after a heat treatment at 286$\celsius$ and slow cooling.