Vanadium dioxide (VO2) metal conducts electricity — with ten times less heat

 

A team of researchers led by the Lawrence Berkeley National Laboratory recently discovered a metal that conducts electricity without producing or requiring excess heat. While it would not be a far-fetched notion in conductors operating at cryogenic temperatures, it is an unusual property for one that operates at a temperature of approximately 67 degrees Celsius.

The metal vanadium dioxide (VO2) accomplished just that. Researchers discovered that passing an electrical current through nanoscale rods of VO2 resulted in ten times less heat than the Wiedemann-Franz Law would predict. “This was a totally unexpected finding,” said Berkeley physicist and professor Junqiao Wu. “It shows a drastic breakdown of a textbook law that has been known to be robust for conventional conductors. This discovery is of fundamental importance for understanding the basic electronic behavior of novel conductors.”

At the nanoscale level, heat is carried primarily by vibrations in the crystal lattice. At ordinary temperatures, waves of phonons travel through metals and interfere with electrons’ ability to freely pass through the structure. At ultra-low temperatures, however, atoms are nearly frozen into immobility, which results in the free flow of electrons with almost no rise in temperature. For this reason, most metals become superconductors at cryogenic levels.

 

Vanadium dioxide, however, undergoes an abrupt transition at 67 degrees Celsius, transforming its crystal structure and changing from an insulator to a conductor. With a remarkably low thermal energy release, electrons in VO2 flow freely to produce a current without limited movement. Researchers theorize that this is because VO2 in its transition phase is a “non-Fermi liquid.”

According to the Fermi Liquid Theory, low temperatures cause electrons in most metals to collect other electrons on the path through the material, accumulating a mass as quasiparticles. These quasiparticles are subject to high dissipation rates at room temperature. Non-Fermi liquids, however, behave differently. Rather than producing quasiparticles for the transport of heat, these materials generate current as electron diffusion moves like liquid from areas of high-electron density regions to low-density regions.

Professor Wu discussed this further in relation to VO2, stating, “The electrons were moving in unison with each other, much like a fluid, instead of as individual particles like in normal metals. For electrons, heat is a random motion. Normal metals transport heat efficiently because there are so many different possible microscopic configurations that the individual electrons can jump between. In contrast, the coordinated, marching-band-like motion of electrons in vanadium dioxide is detrimental to heat transfer as there are fewer configurations available for the electrons to hop randomly between.”

 

Berkeley Lab scientists Junqiao Wu, Fan Yang, and Changhyun Ko (l-r) are working at the nano-Auger electron spectroscopy instrument at the Molecular Foundry, a DOE Office of Science User Facility. They used the instrument to determine the amount of tungsten in the tungsten-vanadium dioxide (WVO2) nanobeams. (Credit: Marilyn Chung/Berkeley Lab)

 

The metallic vanadium dioxide was also discovered to have its electricity-to-heat ratios altered by producing an alloy with other metals. Combining a single crystal of VO2 with tungsten resulted in improved electron flow and a decreased temperature at which the transition into a conductor occurred.

Co-lead author Fan Yang, a postdoctoral researcher at Berkeley Lab’s Molecular Foundry, stated, “This material could be used to help stabilize temperature. 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.”

Yang added that more questions need to be answered before the metal can be commercialized, though the study highlights the potential for “exotic electrical and thermal properties.” Researchers will continue experimenting with and studying the metal, while also debating whether it qualifies as a non-Fermi liquid at its transition point.

Did you miss this?

Other Popular Stories

  • Are we ready to let go of the wheel? The current state of self-driving car technology.
  • Pratt & Whitney Canada to invest $275 million in Quebec plant
  • China Opens Solar Highway, Closes in Under a Week
  • Canadian oil production up; producers turning to railways for shipment
  • Building permits shot up in May
  • Calgary company a leader in waterless fracking
  • Construction industry pleased with majority government in Ontario
  • Bombardier to build more commuter trains for London transit
  • Siemens Canada announces order for 270-MW wind project in Ontario
  • Nexen Energy Expansion Announced
  • Fracking study finds methane emissions lower than EPA estimates
  • Manufacturing output grew again in August
  • Scientists create liquid fuel from solar energy
  • GM restructuring goes forward with agressive job cuts in Ontario designed to save billions of dollars — at the same time they recruit new hires?
  • Inter Pipeline will spend $2.6 billion to transport bitumen to oil sands projects
  • Drilling rigs growth depends more and more on LNG
  • Final testing of Bombardier's C Series to begin
  • Federal government urged to speak up for nuclear at Paris climate talks
  • Why a Russian submarine may have tried to tap into undersea communications: 95 percent of communications and $10 Trillion in data are carried on undersea cables
  • Lockheed Martin seeking industry partners in new innovation and research facility
Scroll to Top