Saturday, July 20, 2024

Crystals Of Silicon and Rhenium Make Transverse Electricity From Heat

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Researchers discovered that a layered crystal of silicon and rhenium can produce electricity with notable efficiency.

There is a term in physics called thermoelectricity which refers to the direct conversion of heat into electricity and vice versa through two related mechanisms, the Seebeck effect and the Peltier effect. The Seebeck effect is a phenomenon in which a voltage difference is produced as a result of a temperature difference between two dissimilar electrical conductors or semiconductors. In other words, when heat is applied to one of the two conductors or semiconductors, the high energy electrons flow from the hotter one to the cooler one. The Peltier effect is a reverse phenomenon in which heat is emitted when electric current passes across a junction between two conductors or semiconductors.

Transverse thermoelectricity can simplify energy harvesting from heat as the electric field and heat gradient are perpendicular. Now, the transverse thermoelectricity has been earlier demonstrated by the researchers but the power output is much less than in standard devices. Researchers from the Ohio State University have demonstrated transverse thermoelectric generation with notable efficiency.

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The researchers developed a crystal of rhenium and silicon that can produce electricity at right angles to heat flowing through it. It works when the internal structure of the crystal is at a specific angle to the heat flow, causing electrons and holes separate and travel off in opposite directions at right angles to the heat. 

“We showed that these materials are as effective as conventional thermoelectric generator technology, with efficiencies that are orders of magnitude higher than any previous transverse device. This compound is just as good as what you can buy commercially.” said chemistry professor Joshua Goldberger.

After discovery of such crystals, scientists searched for the similar materials and now they have experimentally confirmed 15 materials with these properties. 

“A few had been discovered, but none was exploited for functionality. What we have found is that we can actually do something with it,” said Ohio professor of materials science Wolfgang Windl. “All we have to do is put wires to one end and orient the crystal a certain way and suddenly we have a power generator with no moving parts.”

The work ‘Highly efficient transverse thermoelectric devices with Re4Si7 crystals‘ is published in Energy & Environmental Science.



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