An international team of researchers has found that ice can generate electricity when bent or unevenly deformed.
Scientists have known for a long time, that lightning is generated electricity when ice particles collide within clouds. However, until now, there has been no clear understanding, of how these particles receive an electrical charge, as ice does not generate electricity when it is simply compressed.
A new study has found, that the uneven deformation of ice during such collisions of ice particles in clouds is sufficient to generate electrical charges. The study was conducted by researchers from the Catalan Institute of Nanoscience and Nanotechnology (ICN2), Xi’an Jiaotong University and Stony Brook University. The researchers also found, that electrical properties of ice vary with temperature.
“This work changes the way we think about ice: from a passive material, it turns into an active material. That can play an important role in both basic research and practical applications”, — says the study’s lead author, nanophysicist from the Catalan Institute Xin Wen.
Unlike piezoelectricity, when electric charges are generated by changing the polarity of a material under the influence of voltage, flexoelectricity can occur in materials with any symmetry. This fully explains the unusual behavior of ice.
As part of the experiment, the researchers placed a plate of ice between the two electrodes. They carefully checked, that the generated electric charges were not piezoelectric. When the plate was bent, it generated electricity at all tested temperatures.
“In our study, we measured the electrical potential, that occurs when an ice plate is bent. Specifically, the bar was placed between two metal plates and connected to a measuring device. The results coincide with those previously observed when ice particles collide during thunderstorms”, — explains Prof Gustau Catalan, who leads a group of researchers from the Department of Oxide Nanophysics at the Catalan Institute.
The researchers also found, that at temperatures below -113°C, a thin ferroelectric layer forms on the ice surface. As noted by Xin Wen, the surface of the ice can form a natural electric polarization, which can be reversed, using an external electric field — just as the poles of a magnet can be reversed.
“Ice can have not one, but two ways of generating electricity: ferroelectricity at very low temperatures and flexoelectricity at higher temperatures, down to 0°C”, — says Xin Wen.
These results place ice alongside promising electrochemical materials, such as titanium dioxide, which are widely used in sensors and capacitors. The ability to switch between flexoelectricity and ferroelectricity demonstrates the unexpected versatility of ice.
“With this new knowledge of ice, we will revisit ice-related processes in nature to find out if there are other significant effects of ice flexoelectricity that have been ignored all this time”, — Xin Wen notes.
The results of the study are published in the journal Nature Physics
Source: NotebookCheck; Interesting Engineering
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