Electric field steers heat through ceramic in lab study
Oak Ridge researchers say an electric field made a ferroelectric ceramic conduct heat nearly three times better along one direction.
By Lucas Ferreira · Science & Environment Writer
3 min read
Researchers at the Department of Energy’s Oak Ridge National Laboratory and partner institutions report that an applied electric field made heat move almost three times more efficiently in one direction through a specialized ceramic. The finding, published in PRX Energy, points to a possible way to improve cooling systems, energy devices and electronics that depend on tight thermal control, ORNL said.
The work was carried out with The Ohio State University and Amphenol Corporation, according to ORNL. The team studied how electricity changes phonons, the atomic vibrations that carry heat through solids.
How the field changed heat flow
The researchers focused on relaxor-based ferroelectric ceramics, a class of materials in which small electric charges can line up under an external electric field. ORNL said that alignment reduced disruptions that would normally scatter heat-carrying phonons as they move through the crystal.
In the experiments, phonons traveling along the field’s poling direction lasted much longer than vibrations traveling across it, according to the study. The team connected that longer survival time to the nearly threefold increase in heat conduction along the preferred direction.
ORNL said the electric field affected both the speed of the phonons and how long they persisted before scattering. Michael Manley, an ORNL senior researcher who helped lead the neutron scattering measurements, said earlier work on bulk ferroelectric materials had produced thermal-conductivity gains of only 5% to 10%, while the new measurements showed an increase close to 300% because phonons traveled farther before stopping.
Neutrons tracked atomic motion
To see what was happening inside the material, the team used inelastic neutron scattering at ORNL’s Spallation Neutron Source, a DOE Office of Science user facility. ORNL said the technique allowed researchers to examine both the positions of atoms in the crystal and how those atoms moved.
Manley and ORNL senior R&D staff member Raphaël Hermann led the neutron scattering experiments, according to the laboratory. The ceramic crystals used in the work were grown and then exposed to the electric field, or poled, by Raffi Sahul at Amphenol Corporation.
The thermal conductivity experiments were designed by the late Ohio State professor Joseph Heremans, ORNL said. Doctoral candidate Delaram Rashadfar carried out the analysis under Heremans’ guidance, and the team combined those measurements with neutron data to link the enhanced heat flow to changes in the material’s atomic vibrations.
Potential uses
ORNL said better control of heat transfer could help technologies such as solid-state cooling systems with no moving parts, devices that convert heat into electricity, chip-based electronics and cogeneration systems that recover industrial waste heat. The laboratory framed the work as a step toward devices that direct thermal energy more efficiently rather than allowing heat to spread without control.
The research was supported by the DOE Basic Energy Sciences program, with additional contributing partners, according to ORNL. The paper lists Puspa Upreti, Delaram Rashadfar, Raffi Sahul, Douglas L. Abernathy, Joseph P. Heremans, Raphaël P. Hermann and Michael E. Manley as authors.
This story draws on original reporting from ScienceDaily.