Dielectric properties of ice VI at low temperatures

Abstract

The limiting low‐frequency permittivity of ice VI at a pressure of about 9 kbar has been measured between 301 and 128 °K to seek evidence for an ordering transformation. In the experimental range, the quantity (ε0 −ε∞) T, where ε0−ε∞ is the orientation polarization, increased by a factor of 1.49, and follows a Curie–Weiss law with an apparent ordering temperature of 47 °K. Ice VI appears, therefore, to be approaching a ferroelectrically ordered state at low temperature. However, neutron diffraction measurements (Ref. 14) indicate that ice VI recovered at ∼100 °K and atmospheric pressure is partly ordered in an antiferroelectric manner, and so there is presumably an unobserved transformation between the conditions of 128 °K and 9 kbar and 100 °K and 1 bar. The relaxation time follows an Arrhenius law with constant activation energy down to the lowest temperatures, in contrast to ice Ih, in which the activation energy drops to about a half below a temperature that depends on the sample. No doubt the impurities that cause the drop in ice I are too insoluble in ice VI to affect its relaxation time.