Electricity Conducted Without Heat Discovered With Vanadium Dioxide

A type of material that is said to be a good conductor of electricity is also a good conductor of heat. That is what the Wiedemann–Franz law states. But researchers have discovered a new property in one type of metal that defies this law. Scientists at Lawrence Berkeley National Laboratory (Berkeley Lab), and the University of California found that the metallic form of vanadium dioxide conducts electricity without conducting a proportional amount of heat. Actually, vanadium dioxide conducts electricity 10 times more than heat!

 

vanadium dioxide - produces electricity but no heat

Vanadium dioxide (VO2) nanobeams synthesized by Berkeley researchers show exotic electrical and thermal properties. In this false-color scanning electron microscopy image, thermal conductivity was measured by transporting heat from the suspended heat source pad (red) to the sensing pad (blue). The pads are bridged by a VO2 nanobeam. (Credit: Junqiao Wu/Berkeley Lab) Source: http://newscenter.lbl.gov/2017/01/26/electricity-not-heat-flows-in-vanadium-dioxide/

 

Implementing a metal that conducts electricity without heat has many possible applications. One possibility would be for a thermoelectric system. Engines and appliances conduct heat when used. A metallic form of vanadium dioxide could actually be used one day to transfer the wasted heat energy from these things back into electricity!

 

How Does Vanadium Dioxide Conduct No Heat?

The scientists explored the metallic form of vanadium dioxide and found that the electrons move simultaneously with each other, as opposed to individually, “hopping” around. Think of it this way: electrons in vanadium dioxide move together like a fluid, and electrons in other metals move about freely, or at random. Because of this fluid-like movement, electrons in vanadium dioxide conduct electricity well (maintain directional movement), but don’t conduct heat well because the amount of random movement is low. 

 

In the past, other scientists figured out how to conduct electricity without heat using other material, but these materials wouldn’t be useful in a practical sense because in order for this to occur, they required to be at temperatures hundreds of degrees below zero. 

 

Other Cool Things About Vanadium Dioxide

Vanadium dioxide is also known to switch from an insulator to a metal by reaching 152 degrees Fahrenheit. It is also transparent at room temperature.

 

By mixing different materials with vanadium dioxide, it is possible to adjust the amount of heat and electricity it conducts. The scientists at the Berkeley Lab and the University of California decided to add the metal tungsten to the vanadium dioxide. With the added tungsten, the electrons in the metallic vanadium dioxide became a better heat conductor.

 

“This material could be used to help stabilize temperature,” says Fan Yang, a researcher at Berkeley Lab’s Molecular Foundry. “By tuning its thermal conductivity, the material can efficiently and automatically dissipate heat in the hot summer because it will have high thermal conductivity, but prevent heat loss in the cold winter because of its low thermal conductivity at lower temperatures.”

 

Sources:

For This Metal, Electricity Flows, But Not the Heat