Electrical Conductivity and Relaxation in Ice Crystals with Known Impurity Content

Abstract

Abstract Three-terminal dielectric bridge measurements (in the range 20 Hz to 100 kHz between — 5°C and —90 to — 120°C) have been made of ice doped with (a) conductivity-enhancing ionic impurities (HCl, HF, NaCl, KF, NH4F) and (b) conductivity-depressing solutes (NH4OH, NH4Cl, NH5CO3, NaHCO3). Blocking electrodes were used for the first group. The true ice parameters were extracted from linearized plots of the Debye equations. Chlorides and fluorides showed very similar characteristics in their spectra and static conductivity. The results suggest that static conductivity is controlled by extrinsic protons. On the other hand, bases, or solutes that impart a positive freezing potential to the ice, suppress extrinsic protons. In this case, the static conductivity was not, or only weakly, temperature dependent and lower than in the first group. A conductivity cross-over was observed in neither case. The dielectric conductivity contribution is strongly dependent on impurity concentration but apparently less affected than the static conductivity by the nature of the solute. The principal relaxation time is reduced by most solutes, exceptions are pure (bicarbonate-free) bases, sodium bicarbonate, and carbon dioxide.