Enhanced electroactive β-phase and dielectric properties in P(VDF-HFP) composite flexible films through doping with three calcium chloride salts: CaCl2, CaCl2<middle dot>2H2O, and CaCl2<middle dot>6H2O

Flexible dielectric films with a high dielectric constant, utilizing P(VDF-HFP)/salt composites, were manufactured through the solution casting method. In this work, we studied the impacts of three calcium chloride salts-CaCl2, CaCl2<middle dot>2H(2)O, and CaCl2<middle dot>6H(2)O-on the surface morphology, crystalline phase transformation, mechanical properties, and dielectric responses of the P(VDF-HFP) copolymer. The detailed structure and properties of all samples were assessed via scanning electron microscope (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), tensile testing, and LCR meter analysis. The experimental results demonstrated that the addition of calcium salts to the P(VDF-HFP) composites induced a visibly microporous morphology, with the porosity and surface roughness of the composites gradually increasing with salt content. In comparison to the pure P(VDF-HFP) film, the composite films exhibited decreased stiffness and heightened flexibility. Furthermore, a higher beta-phase fraction and notable enhancements in the dielectric constant resulting from the inclusion of calcium salts were observed. Consequently, the P(VDF-HFP) composite filled with 3 wt% of CaCl2<middle dot>6H(2)O demonstrated the highest capability for promoting the beta-phase fraction and dielectric constant, achieving values of 98.33% and 21.49% (at 10 Hz), respectively.