Large Electrocaloric Effect in Stretched Relaxor Ferroelectric Polymers near Morphotropic Phase Boundary

Use of the morphotropic phase boundary (MPB) is a promising approach to enhance the electrocaloric effect in ferroelectric polymers. This is usually achieved by a composition method, and polymer processing near the MPB to tune electrocaloric response has attracted little attention. Here, the relative stability between disordered 3/1-helix and ordered all-trans conformations is leveraged by uniaxial stretching to improve the electrocaloric effect in relaxor ferroelectric polymers under low electric fields. It is found that the stretching technique enables a considerably more enhanced electrocaloric response in polymer composition near the MPB at room temperature, compared with counterparts corresponding to the relaxor phase. The electrocaloric-induced temperature change is found to be 4.5 K under a low electric field of 50 MV m−1 in stretched relaxor ferroelectric polymers at room temperature, corresponding to a 60% enhancement over pristine counterparts. This result highlights the critical role of polymer processing in optimizing electrocaloric properties, especially near the MPB, and this can be extended to improve other functionalities, such as piezoelectric response, in relaxor ferroelectric polymers.