Processing-Enhanced β-Phase Formation in BaTiO₃/PVDF Composite Fibers with High Electroactive Phase Content

Flexible piezoelectric fibers are promising materials for next-generation wearable and flexible electronic devices due to their lightweight structure, mechanical flexibility, and electromechanical response. In this study, BaTiO₃/PVDF composite fibers were prepared by melt spinning under an electrostatic field, followed by thermal drawing to enhance the electroactive phase content. The effects of BaTiO₃ loading, draw ratio, thermal stretching ratio, stretching rate, and electric field strength on the crystalline structure of the fibers were systematically investigated. Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and electron microscopy were used to evaluate phase evolution, crystallinity, and filler distribution. The results showed that the processing conditions significantly influenced the transformation of PVDF from the α-phase to the electroactive β-phase. The optimized fibers were obtained at 1 wt.% BaTiO₃, a thermal stretching ratio of 5, a stretching rate of 40 mm/min, and an electric field strength of 18 kV, resulting in a crystallinity of 61.3% and a β-phase content of 95.5%. The enhanced structural characteristics indicate the strong potential of the developed composite fibers for flexible electroactive applications, though direct electromechanical characterization is required for device integration.