Phase Engineering for Enhanced Piezoresponse in P(VDF-TrFE) and Its Composites

The negative piezoelectricity in ferroelectric polymers cannot be fully explained by their crystal structure alone. The semi-crystalline nature of these materials suggests a coupling between the intermixed crystalline and amorphous phases. In this study, the role of the phase boundary gradient - a transitional zone of diminishing crystallinity - in enhancing the piezoresponse of P(VDF-TrFE) and its composites is investigated. Using X-ray diffraction (XRD) and advanced piezoresponse force microscopy (PFM) techniques, the effects of thermal treatments and ceramic filler incorporation on the material's nanostructure and electromechanical behavior are examined. These findings reveal that controlled thermal processing within the ferroelectric temperature range modifies the P(VDF-TrFE) nanostructure, resulting in an enhanced piezoresponse despite a decrease in overall crystallinity. This phenomenon is attributed to the expansion of phase boundary gradient regions, contributing to the negative piezoelectric effect. In composites containing barium titanate, radially varying piezoresponse patterns are observed, suggesting the formation of an extended boundary gradient at the polymer-filler interface. The concept of phase boundary engineering presents implications for the design and optimization of high-performance flexible ferroelectrics, potentially leading to advancements in various applications such as sensors, actuators, and energy harvesting devices.