Possible Phase Transition in H$_{2}$O Ice Ih near 110 K

The thermal expansion of single-crystalline H$_{2}$O ice Ih was measured with $\sim$$10^{4}$ times greater relative resolution than has previously been done. Plots of the thermal expansion coefficient, \textit{$\mu$}, along the a- and c-axes reveal features which have \textit{never before been observed} in thermal expansion measurements of H$_{2}$O ice: \begin{itemize} \item A jump in $\mu$ of magnitude $\Delta$\textit{$\mu$} $\approx$ $10^{-5}$ $K^{-1}$ in the temperature range 98--117 K along the c-axis, which appears to be a phase transition. No such transition is observed along the a-axis. \item Hysteresis of the transition temperature, \textit{T$_{c}$}, of as much as 5 K for cooling rates from -5.0 to -0.1 K/min. \end{itemize} There is reason to believe this transition is the ferroelectric transition reported by Dengel et al.\footnote{Dengel et al., \textit{Physics Letters}, \textbf{9}, pp. 291-292, 1964.} If so, the shift in \textit{T$_{c}$} would result from the freezing-in of the H$_{2}$O molecular configurations. We will discuss our own measurements of the dielectric constant in the vicinity of \textit{T$_{c}$}.