Dec 02, 2019 15:05:00

Contrary to the laws of physics, physicists specify 'substances that allow electricity but not heat'

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One of the laws of physics is that 'a substance that conducts electricity well can easily conduct heat' is known as the Weedmann-Franz law . However, contrary to the Wiedemann Franz law, it was discovered that 'a substance that conducts electricity but does not transmit heat' was discovered.

Anomalously low electronic thermal conductivity in metallic vanadium dioxide | Science
https://science.sciencemag.org/content/355/6323/371

Physicists Have Identified a Metal That Conducts Electricity But Not Heat
https://www.sciencealert.com/physicists-identify-a-metal-that-conducts-electricity-but-not-heat

Through experiments conducted by Japanese researchers, it has been confirmed that

vanadium dioxide has the property of ' changing from an insulator to a conductor when heat or static voltage is applied '. Therefore, a research group such as Junqiao Wu et al., Who is studying materials engineering at the University of California, Berkeley, studied how electrons move through the crystal structure in vanadium dioxide in order to investigate the properties of vanadium dioxide in more detail. An experiment was conducted to confirm how much heat was generated in

Below is an electron micrograph of the experiment, showing that a fine vanadium dioxide rod connects the heat source pad (left) and the detection pad (right).

In this experiment, the research group calculated the thermal conductivity that could be attributed to electrons in vanadium dioxide and found that it was only one-tenth of the value derived by Weedmann-Franz law. Wu said, “In normal metals, heat is efficiently transferred by randomly moving free electrons in the metal, but the electrons in vanadium dioxide move in an orderly manner like a

marching band. It is thought that there will be a phenomenon in which heat is difficult to be transmitted even though it flows. '

The research group also found that it is possible to adjust the way electricity and heat are transmitted by mixing vanadium dioxide with another substance. For example, when tungsten was added to vanadium dioxide, the temperature required to change vanadium dioxide into a metal that conducts electricity well decreased, and the thermal conductivity was improved.

Fan Yang, a co-author of the paper, said, “Vanadium dioxide may help keep the room temperature constant without using an air conditioner. During this time, the room temperature is efficiently dissipated due to the high thermal conductivity, and when the temperature drops in winter, the thermal conductivity decreases and the heat loss can be prevented. '

by Sergei Akulich