Conductivity is a measure of how easy heat or an electric charge travels through a material. Materials can be classified as insulators, semiconductors, and metals but how do you classify a metal that only conducts electricity and not heat?
Well, according to the lead researcher from Berkley’s Lab Materials Sciences Division, Junqiao wu, VO2(Vanadium Dioxide)—an already mysterious metal known for its out of the box abilities of transforming from a transparent insulator into a conductive metal at 152 Fahrenheit or 67 degrees’ Celsius, can conduct electricity pretty well at temperatures above room temperature.
VO2 is normally a conductor at temperatures above room temperature making its applications diverse and practical at the same time. Sure, there are other handful of materials that are better conductors of electricity than heat but these properties are only available at temperatures significantly below zero which renders them highly impractical in real world situations.
Vanadium dioxide throws out Wiedermann-Franz law out the window. The law arises from the fact that the electrons in a metal can carry both heat and charge. Which makes VO2 a dog whistle alerting scientists its unconventional and puzzling nature.
In an interview, Junqiao Wu said that VO2 collapses Wiedermann-Franz law which has been a pinnacle to understanding conventional conductors. He added that this could be the foundation for comprehending the primary principles of new conductors and their electronic behavior.
This anomalous property of Vanadium Dioxide changes our knowledge of conductors and paves the way for a wide range of unprecedented real-world applications. From enhanced insulation of window coverings to repurposing wasted heat energy from engines to electricity.
To unearth this atypical behavior, the team observed the movements of electrons within the metal’s crystal lattice and the amount of heat dissipated. To their surprise, they found out that the thermal conductivity that could be credited to the electrons was up to 10X smaller than what they would expect with the Wiedemann-Franz law.
This could be attributed to the harmonized movement of electrons within the material. According to Wu, the electrons traveled in an atypical way similar to fluids which are different from normal metals which transport heat in numerous micro-configurations which the electrons can bounce between.
This makes the atypical nature of VO2 detrimental to the transfer of heat thanks to its small number of micro-configurations. Additionally, when the researchers combined VO2 with other materials they were able to modify the amount of heat and electric charge that could be conducted.
In an experiment, they added tungsten to VO2 and were able to enhance its heat conductivity when they reduced the temperature required for the material to be metallic. The experiment revealed that VO2 could be used as an insulator and a heat conductor when the temperature rose above a predetermined temperature.
Furthermore, since VO2 can be transparent at 30 degrees Celsius it can successfully reflect infrared light while still being transparent at around 60 degrees Celsius. This means that it can be used a window coating for insulation without using an air conditioner.
This fascinating nature of this material at room temperature makes it applicable in diverse real-world situations but further testing is needed before it can hit the shelves.