Thermoelectricity at a gallium-mercury liquid metal interface

TL;DR

This study demonstrates a thermoelectric effect at a liquid metal interface, revealing high current densities and flow behaviors influenced by magnetic fields, with implications for liquid metal battery efficiency.

Contribution

First experimental demonstration of thermoelectricity at a liquid-liquid metal interface, including flow dynamics and magnetic field effects, expanding understanding beyond solid-state systems.

Findings

High current densities near boundaries due to thermal gradients.

Magnetic fields induce azimuthal shear flows with distinct regimes.

Model aligns with observed flow patterns and thermoelectric currents.

Abstract

We present experimental evidence of a thermoelectric effect at the interface between two liquid metals. Using superimposed layers of mercury and gallium in a cylindrical vessel operating at room temperature, we provide a direct measurement of the electric current generated by the presence of a thermal gradient along a liquid-liquid interface. At the interface between two liquids, temperature gradients induced by thermal convection lead to a complex geometry of electric currents, ultimately generating current densities near boundaries that are significantly higher than those observed in conventional solid-state thermoelectricity. When a magnetic field is applied to the experiment, an azimuthal shear flow, exhibiting opposite circulation in each layer, is generated. Depending on the value of the magnetic field, two different flow regimes are identified, in good agreement with a model based on the spatial distribution of thermoelectric currents, which has no equivalent in solid systems. Finally, we discuss various applications of this new effect, such as the efficiency of liquid metal batteries.