Phase-change materials and their applications Free

Phase-change materials (PCMs) undergo reversible, drastic changes of their properties in response to external stimuli, including thermal, optical, mechanical, or electrical signals. The process normally absorbs (or releases) significant amounts of latent heat within the transition. In addition to their applications in energy-related fields, phase-change materials can also restore a preset shape at a specific temperature due to their shape memory effect, which opens new possibilities for wearable devices, non-volatile memories, and optical storage media. Most of the research on PCMs relates to studies that aid in our understanding their underlying physics and thus is focused on fundamental materials research. On the theoretical side, it mainly includes the in-depth study of the fundamental physical properties and structural transformations of materials, such as thermodynamic behaviors and crystal structures, aiming to better understand and utilize the whole phase transition process. Although there are still many phenomena that need to be fully understood, the time has now come to increase the efforts in transitioning from fundamental research efforts to the use of the drastic material property changes that accompany the phase-change in the strategic design of devices that can provide performance that is beyond the theoretical limits of traditionally used mechanisms.

Some of the applied research efforts in PCMs include new formulations and phase transition-induced techniques to improve their stability and efficiency. Specific areas of application include thermal energy storage systems, smart building and textiles, as well as electronic devices and systems. Additionally, there is ongoing work on creating special PCMs tailored for niche uses, such as those with enhanced performance characteristics or those designed for use in extreme environments. In summary, although the underlying physics of some phase-change materials is yet to be fully understood—casting a shadow on the full potential of devices/systems relying on phase-change materials—progress on the applied physics aspect of the field is now feasible and even necessary for some applications. This Special Topic aims to demonstrate the integration of phase-change materials into sensors and actuators that exploit their multifunctionality, and fundamental studies that help us understand them.

This “Phase-change Materials and Their Applications” Special Topic in the Journal of Applied Physics provides an overview of the new research, new discoveries, and new applications in the field of phase-change materials. Specifically, highlighted topics include the theory, modeling, and simulation of solid-to-solid phase transitions (Refs. 2, 6–8, 19, 11, 12, 14, 18, and 25), the utilization of phase-change materials in terahertz (THz) devices/systems (Refs. 4 and 17), advances in vanadium oxides (Refs. 3–5, 9, 13, 15, 17, 18, 21, and 27), developments in thermal energy storage management (Refs. 1, 12, 20, and 23), dielectrics, ferroelectrics, and multiferroics (Refs. 10 and 22), investigations into thin films, interfaces, and surfaces (Refs. 3–5, 9, 14, 15, and 26), effect of element ratio on phase-change materials (Refs. 18, 24, and 26), and applications in the Electronics Field (Refs. 1, 5, 13, and 16). These studies aim to deepen our understanding of the fundamental physics underlying phase-change materials and to showcase their multifunctional capabilities in various technological applications.

The guest editors express their sincere gratitude to the staff and editors of the Journal of Applied Physics for their efforts in compiling this Special Topic and all the authors and reviewers for their contributions.