Growth of ferroelectric ice XI doped with alkali metal hydroxide observed using neutron diffraction

Arakawa, Masashi*; Komatsu, Kazuki*; Iizuka, Riko*; Kagi, Hiroyuki; Fernandez-Baca, J. A.*; Chakoumakos, B.*; Yamauchi, Hiroki   ; Fukazawa, Hiroshi

We prepared ice XI from different kinds of alkali metal hydroxide solutions with different concentrations, and measured neutron powder diffraction at JRR-3 (Japan Atomic Energy Agency, Japan) and HFIR (Oak Ridge National Laboratory, TN, USA). Rietveld analysis was carried out for the obtained diffraction patterns using a two-phase model, which includes ices Ih and XI. The hydrogen-ordered structure in the lithium-doped ice was the same as that in the sodium-doped and potassium-doped ices. We also confirmed the optimum formation condition of ice XI for the temperature history and concentration of solution. Furthermore, our results indicate that the phase transition from ice Ih to XI occurs in the doped ice that had once been ice XI to a notably larger degree than in the doped ice that had never transformed to ice XI. We named this phenomenon memory effect of hydrogen ordering.