Morphotropic Phase Boundary in Irradiated Ferroelectric Polymers

Morphotropic phase boundary (MPB) enables a large piezoelectric effect in ferroelectric polymers. However, till now MPB has only been observed in a few polymers, which is induced by compositional tuning of the polymer composition. Here a distinct approach to design MPB in ferroelectric polymers is reported via ion irradiation. Without changing composition as required by the conventional compositional approach, the formation of helix/trans MPB in ferroelectric polymers is achieved upon increasing the irradiation dose, near which a substantially enhanced piezoelectric coefficient d₃₃ of -69.8 pC N^-1 is observed. The effectiveness of this method is demonstrated by using different sources of irradiation and polymer compositions, which offers a general and scalable postprocessing tool to effectively improve the piezoelectric response of ferroelectric polymers.