Applying an electric field to relaxor-based ferroelectric ceramics can increase thermal conductivity along the field direction by nearly 300 percent. This finding, from work at Oak Ridge National Laboratory and its collaborators, rests on precise measurements that reveal how the field alters microscopic behaviour in the material.
The mechanism is straightforward yet striking. The electric field aligns internal charges. This alignment suppresses nanoscale antiferroelectric instabilities along the field direction. As a result, phonon lifetimes lengthen and scattering decreases. Phonons, the quantum packets that carry heat, travel farther before colliding.
Thermal conductivity along the field direction therefore triples compared with the perpendicular direction. The improvement holds across a broad temperature range, making it more than a narrow laboratory curiosity.
Earlier work on bulk ferroelectric materials achieved modest improvements in thermal conductivity of 5 percent to 10 percent, while the new measurements reveal an enhancement close to 300 percent — mainly because the phonons are able to travel much longer before they stop.
Michael E. Manley, a researcher at Oak Ridge, offered that assessment. His comment underscores the scale of the advance. Previous attempts on conventional ferroelectrics managed only small gains. The new work, centred on a composition such as PMN-30PT, delivers an order-of-magnitude larger effect.
Neutron scattering and transport data
Confirmation came from two independent techniques. Inelastic neutron scattering at the Spallation Neutron Source provided direct insight into phonon dynamics. Separate thermal transport measurements quantified the macroscopic conductivity. Together they paint a consistent picture.
The result stands in contrast to earlier studies. Those recorded improvements of just 5 to 10 percent. Here the enhancement reaches close to 300 percent. Such a jump suggests the suppression of local instabilities plays a decisive role.
