Researchers at the Department of Energy's Oak Ridge National Laboratory (ORNL), working with The Ohio State University and Amphenol Corporation, have discovered a surprising new way to control how heat moves through solid materials — using electricity to boost heat conduction by nearly 300% in a preferred direction.
The findings, published July 11, 2026, in PRX Energy, challenge long-held assumptions about heat transport and could lead to radically more efficient cooling systems, energy devices, and electronic technologies.
How It Works
The study found that applying an electric field to a specialized class of ceramics called relaxor-based ferroelectrics changes the behavior of phonons — the tiny atomic vibrations responsible for carrying heat. When the atoms vibrate in the same direction as the electric field (known as the poling direction), those phonons persist much longer than vibrations moving across it.
As a result, heat travels almost three times more efficiently along the direction of the electric field than it does in other directions.
"Being able to control both how fast and in what manner heat flows could lead to devices that manage thermal energy far more efficiently," said Puspa Upreti, an ORNL postdoctoral research associate and co-author of the study.
Neutron Experiments Reveal the Mechanism
To understand exactly what was happening inside the material, the team conducted experiments at ORNL's Spallation Neutron Source, a DOE Office of Science user facility. Using advanced inelastic neutron scattering techniques, the researchers observed both the positions of atoms within the crystal and how those atoms moved.
The measurements showed that applying an electric field not only increased the speed of the phonons but also significantly extended how long they survived before scattering. Those longer lifetimes are the key reason the material became so much better at conducting heat.
"Earlier work on bulk ferroelectric materials achieved modest improvements in thermal conductivity of 5% to 10%, while the new measurements reveal an enhancement close to 300% — mainly because the phonons are able to travel much longer before they stop," said ORNL senior researcher Michael Manley, who led the inelastic neutron scattering experiments.
Why It Matters
The ability to direct heat efficiently is essential for many advanced technologies, including: - Solid-state electronic cooling systems with no moving parts - Thermoelectric devices that convert heat into electricity - Chip-based electronics that need precise thermal management - Cogeneration systems that capture and reuse waste heat from industrial processes
Better control over heat transfer can improve both performance and energy efficiency across all these applications. The concept is illustrated by the Carnot cycle, the idealized model that defines the maximum theoretical efficiency of a heat engine — which depends critically on carefully regulating the movement of heat between hot and cold regions.
In the new study, the electric field reduced obstacles that normally interfere with phonon movement, allowing the heat-carrying vibrations to travel farther through the material — much like easing congestion on a busy highway.
A Threefold Increase That Surprised Even the Researchers
The crystals used in the experiments were carefully grown and then exposed to the electric field by Raffi Sahul at Amphenol Corporation. The late Professor Joseph Heremans of Ohio State designed the thermal conductivity experiments and guided doctoral candidate Delaram Rashadfar through the analysis.
"While earlier work led us to expect only a modest effect, observing a threefold difference turned out to be a significant result," said Rashadfar. "Professor Heremans always stressed the importance of trusting the data first and letting the theory follow."
The research was supported by the DOE Basic Energy Sciences program.
