Study of the low-temperature ’’transition’’ in ice Ih by thermally stimulated depolarization measurements

Abstract

Thermally stimulated depolarization (TSD) current has been measured in polycrystalline H₂O and D₂O ice in the temperature range 77–260 K and at pressures of about 1 bar and 1.2 kbar. Three peaks in current have been observed at about 1 bar at a heating rate of 0.0023 K sec⁻¹, the smallest of which appears at 110.4 K and 123.8 K in H₂O and D₂O ice, respectively. An increase in heating rate shifts the current peaks to higher temperatures, as does an increase in pressure. From an analysis of the current–temperature plots, the dielectric permittivity and the relaxation times have been obtained. It is shown that the current peak occurring at the lowest temperature is due to the relaxation of frozen‐in orientation polarization of water molecules in ice and does not indicate a thermodynamic transformation to a ferroelectric phase. The equilibrium dielectric permittivity of H₂O ice has been measured in the range 98–119 K by charging the ice for many days and then obtaining the stored charge by TSD technique. The equilibrium dielectric permittivity shows no approach to a ferroelectric ordering at 98 K. The heterocharge in an ice electret of ∼ 10⁵ C V⁻¹⋅F⁻¹ is largely due to the polarization which gives rise to the high‐temperature TSD current peaks. Aging reduces the magnitude of this polarization substantially. The mechanism of this polarization is not clear. The homocharge was seen in one sample of ice as a negative depolarization current. It is proposed that the TSD technique should be useful for the detection of very slow phase transformation in dipolar materials.