Flexible and high dielectric permittivity composites of Na1/3Ca1/3Bi1/3Cu3Ti4O12 and vinylidene fluoride-trifluoroethylene copolymer (P[VDF-co-TrFE])

Abstract

Flexible composites formed by the perovskite Na1/3Ca1/3Bi1/3Cu3Ti4O12 (NCBCTO) with a copolymer of PVDF with TrFE (P[VDF-co-TrFE]) and three phases composites made of NCBCTO, P(VDF-co-TrFE), and multiwall carbon nanotubes (MWCNT) were successfully prepared by solution casting with ultrasound. Their structures were analyzed by wide angle x-rays diffraction (XRD), Fourier Transform infrared (FTIR), and Raman spectroscopy, while their morphology and thermal properties were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The dielectric properties were measured by impedance spectroscopy. All the composites developed predominantly the β-phase; in some of them, the NCBCTO acted as a β-phase nucleating agent, increasing its amount. The addition of NCBCTO altered the Curie temperature of the PVDF-TrFe composites, indicating suppression of the CL-phase. The best combination of high dielectric permittivity with low dielectric loss was displayed by the composite with 75 wt% of NCBCTO and 25 wt% of P(VDF-co-TrFE). The MWCNTs did not contribute to the increase of permittivity, which was attributed to its poor dispersion; instead of behaving as the electrodes of a capacitor, the MWCNT formed a conductive path, probably due to the impeding presence of the NCBCTO particles.