A team from IRG-1, working with collaborators at Argonne National Laboratory and the University of Utah, have demonstrated continuous room-temperature electrical tuning of the thermal conductivity of La_0.5Sr_0.5CoO_3-d by a factor of more than five (a record for a single-step process) via ion-gel gating. Application of a gate voltage in these devices drives a transformation from a metallic perovskite phase to an insulating brownmillerite phase via the formation and migration of oxygen vacancies, realizing the record range of measured thermal conductivities. The ability to control thermal conductivity electrically with a small voltage at room temperature is important for thermal regulation and management in several emergent device concepts.

The team’s approach used a combination of methods, including time-domain thermoreflectance, electronic transport, and X-ray diffraction at the Advanced Photon Source, Argonne National Laboratory, to measure and understand the mechanisms that enable this record tuning of the thermal conductivity.