Abstract
Higher concentrations of ceramic fillers induce brittleness in the ceramic/polymer hybrids which restrict their applications to limited fields especially when such hybrids are prepared for their use as dielectrics. We have synthesized and characterized different BaTiO3-polypyrrole (PPy) composites by changing the concentration of BaTiO3 from 1% by weight of PPy taken to 5 wt % to explore its effect on the dielectric parameters of the final product and found that the BaTiO3-polypyrrole composite with weight ratio of 0.05:1 exhibited highest dielectric constant, lowest dielectric loss and thermally most stable. All the composites were prepared using in-situ polymerization of pyrrole in an aqueous dispersion of low content of BaTiO3 in the presence of small amount of Hydrochloric acid. These composites were characterized for their microstructure and crystallinity by X-ray diffractometer (XRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) while thermal stability by thermo gravimetric (TGA) analysis. An impedance analyser (LCR meter) was utilized to investigate the dielectric parameters. FT-IR data confirmed the presence of the two phases and their interaction, inferred from the shifting of normal PPy peaks. The data obtained from XRD confirmed the presence of crystallites of 2.8 to 5 nm with dominant crystallinity of the filler, TGA analysis (25 to 600 °C) confirmed the higher thermal stability induced on successive addition of the filler into the prepared composites as compared to that of pure PPy in a wide temperature range which is unusual for such a low % age addition of the filler. The SEM analysis together with XRD results reveal that the successive introduction of BaTiO3 particles produced crystallites of 2 to 5 nm size which bonded together and changed the hemispherical shaped larger grains of the matrix to regular shaped smaller grains. The dielectric constant of the composites was enhanced with filler contents from 178 to 522 at 1 MHz for 1 wt % and 5 wt % BaTiO3 respectively. It was concluded that the introduction of BaTiO3 into the polymer matrix with this new procedure has greatly affected the polymerization process, thermal stability, morphology and dielectric properties of the host matrix and has resulted in a novel series of the composites which may have broad applications.
Highlights
The rapid development of the electronic industry can, no doubt, be attributed to the success in the synthesis of ceramic/polymer composites with high dielectric permittivity, semi conductivity and electromagnetic interference shielding [1,2,3,4]. These composites must possess low dielectric losses, convenient and low cost processing conditions and excellent thermal stability to utilize these in the devices which can store electrical energy such as capacitors and batteries [5,6]
For the pure PPy prepared the characteristic N–H bond stretch occurs at 3461 cm−1 whereas the peaks observed at 1560 cm−1 and
FTIR and X-ray diffractometer (XRD) results we can conclude that the polymerization process has greatly been affected by the introduction of the filler (BaTiO3 )
Summary
The rapid development of the electronic industry can, no doubt, be attributed to the success in the synthesis of ceramic/polymer composites with high dielectric permittivity, semi conductivity and electromagnetic interference shielding [1,2,3,4]. The study of ferroelectric particles into the conducting polymer matrix has revealed that there is a decrease in conductivity with the increase in the wt % or vol % of the filler [35] Keeping in view such investigations and focusing the effect of processing conditions on the conductivity of such polymers, the composites using TiO2 in PPy and TiO2 -PVA in PPy [36,37] were successfully prepared and characterized exhibiting excellent dielectric behaviour found both at low and high frequencies of the applied electric field (AC). To the best of our knowledge all these conditions have never been combined to prepare PPy composites
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