Thermoelectrics in ice slabs: charge dynamics and thermovoltages

Thermoelectric effects of ice play an important role in many natural and engineering phenomena. We investigate, numerically and analytically, the electrification of finite-thickness ice slabs due to an imposed temperature difference across them. When exposed to a temperature gradient, thermoelectrification involves a fast initial stage dominated by Bjerrum defects and a subsequent slow stage driven by ionic defects. The time scales of the first and second stages are derived analytically and correspond to the Debye time scales based on the density of Bjerrum and ionic defects, respectively. For a given ice slab, at the steady state, the thermovoltage across it and the charge accumulation near its two ends depend strongly on its thickness, with the sensitivity of the thermovoltage being more pronounced. The discrepancy between the computed thermovoltage and experimental measurements is analyzed. The analysis shows that, although thermoelectric effects in ice were discovered 50 years ago, significant gaps, ranging from the bulk and interfacial properties of defects to the measurement of thermovoltage, exist in the quantitative understanding of these effects. Filling these gaps requires further experimental, theoretical, and computational studies.