Heat is a ubiquitous form of energy that, unlike others, is notoriously difficult to store due to its natural tendency to dissipate. While this property is essential for phenomena like solar energy reaching Earth, it also poses a significant technological challenge. Instead of attempting to confine heat, a team of researchers from the Center for Research in Biological Chemistry and Molecular Materials (CiQUS), in collaboration with the University of Barcelona and the University of Zaragoza, has proposed an alternative strategy: harness heat where it is generated, controlling its flow in real time and using it to develop thermal memory devices.
In a study recently published in Advanced Materials, the team introduces a prototype thermal memory device capable of switching between different thermal conductivity states through the application of small electric voltages. Much like bits in conventional electronics, the system can be programmed to exhibit high thermal conductivity ("on") or low thermal conductivity ("off"), retaining its configuration even after the electrical stimulus is removed.
The device relies on ultra-thin films—just a few nanometers thick—of a hafnium and zirconium oxide with ferroelectric properties. In this material, researchers have combined two key phenomena: the characteristic electric polarization of ferroelectrics and the presence of atomic defects known as oxygen vacancies, which act as barriers to heat transport. The interaction between these two factors enables precise regulation of the system's thermal conductivity.
The underlying mechanism of this behavior is based on electrical control of vacancy movement. Depending on the applied voltage, vacancies either accumulate or disperse within the material, altering how easily heat can propagate. This process results in a hysteretic behavior—similar to that of ferroelectric materials—allowing the definition of two stable and non-volatile thermal states.
While this breakthrough remains at a fundamental stage, far from immediate technological application, the system shows promising features: it operates at relatively low voltages, and the generated thermal states exhibit remarkable stability over time, remaining unchanged for days without appreciable degradation. Among current limitations, the slow switching speed stands out, pointing to areas for future improvement.
This work opens a new pathway for active heat control in solid-state devices, with potential applications in thermal management of electronic systems, energy conversion, and the development of heat-based information processing technologies. In this context, CiQUS holds accreditation as a Research Center of the Galician University System (CIGUS), granted by the Galician Government (Xunta de Galicia), and receives funding from the European Union under the Galicia FEDER 2021-2027 Program.
