There’s a known rule-breaker among materials, and a new discovery by an international team of scientists adds more evidence to back up the metal’s nonconformist reputation. According to a new study led by users and staff at the Molecular Foundry, electrons in vanadium dioxide can conduct electricity without conducting heat. The findings could lead to a wide range of applications, such as thermoelectric systems that convert waste heat from engines and appliances into electricity.
For most metals, the relationship between electrical and thermal conductivity is governed by the Wiedemann-Franz Law. Simply put, the law states that good conductors of electricity are also good conductors of heat. That is not the case for metallic vanadium dioxide, a material already noted for its unusual ability to switch from an insulator to a metal when it reaches 67 degrees Celsius (152 degrees Fahrenheit).
In the course of studying vanadium dioxide’s properties, the team used simulations and X-ray scattering experiments to tease out the proportion of thermal conductivity attributable to the vibration of the material’s crystal lattice, called phonons, and to the movement of electrons. To their surprise, they found that the thermal conductivity attributed to the electrons is ten times smaller than what would be expected from the Wiedemann-Franz Law.