  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.
