Influence of ultrasonic treatment and heating/cooling under electric field on high-k cellulose-barium titanate composites

The present research reports the ultrasonic assisted synthesis of ferroelectric cellulose-barium titanate composites (C/BT). As proved by wide angle X-ray diffraction (WAXD) and by scanning electronic microscopy (SEM), the composites consist of perovskite-type barium titanate particles (BT) of 400- 600 nm, disposed around the cellulose microfibers. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD) revealed the modifications of structure/morphologies of the prepared sample as compared to pristine cellulose, with direct consequences on the polymer crystalline domains, on the uniformity of BT dispersion and on the dielectric properties of the composites. The composites obtained by ultrasonic treatment possess high dielectric constants (58.6-140.5), better breakdown strengths (8.9-17.7 kV/mm) and energy storage densities (2.6-9.0 J/cm3) as compared to BT particles, as well as very low dielectric losses (0.27-3 x 10-4) at industrial frequencies (50-55 Hz), the values being dependent on the content of barium titanate and on the preparation parameters.