A team of scientists at Ohio State University has uncovered the secret behind a property of solid materials known as ferroelectrics. They have found that quasiparticles, known as ferrons, moving in wave-like patterns among vibrating atoms carry enough heat to turn the material into a thermal switch when an electrical field is applied externally. This control of thermal conductivity is due to the material’s structure, rather than any random collisions among atoms.
The study, published in the journal Science Advances, has discovered that the heat-transferring property can be induced by an electric field through a phenomenon known as piezoelectric strain. The lattice contracts or stretches when a voltage is applied, with atoms and forces between them moving back and forth, ultimately changing the material’s mechanical properties and thermal conductivity.
The material used in the study is a common lead zirconium titanate ceramic belonging to the class of piezoelectrics. Ferroelectrics, a subset of piezoelectrics, are materials in which the electrical charges on the atoms can form electrical dipoles that align in the same direction, forming polarization. These dipoles can be switched by an external electric field.
With the use of a simple external electrical stimulus, the thermal conductivity in this type of material can be changed at room temperature, enhancing the possibilities for real-world applications of the technology. The application of an electrical field produced a 2% difference between maximum and minimum conductivity, and the researchers are now studying other materials that might increase that change in thermal conductivity by up to 15%.
The new theory is predictive, allowing researchers to find materials where the effect is much larger and ultimately lead to materials that can be used in heat switches in everyday applications such as the collection of solar power. The researchers are looking for materials that have the right parameters.