Influence of nickel ion-doped mullite composite on electrical properties, phase behavior, and microstructure of poly(vinylidene fluoride) matrix

Abstract

Novel mullite-polymer composite films were prepared by incorporating highly crystallized nickel ion-doped mullite, which acts as filler into polyvinylidene matrix. Various analytical tools had been utilized at room temperature to study the effects of filler on microstructure, phase transformation, and electrical properties of the polymer films. X-ray diffraction spectra (XRD) and Fourier transform infrared spectroscopy (FTIR) confirm the changes of electroactive phase in polyvinylidene fluoride (PVDF) matrix. Two basic factors, which affected the phase transition of the polymer, were (i) the concentration of the dopant ion into the mullite and (ii) the temperature at which doped mullite were sintered. β-phase percentage of doped polymer was found to reach optimum level for the sample doped with nickel ion at concentration of 0.8 M, when sintered at both 1100 and 1400°C. Electrical properties were studied over a wide range of frequency (from 200 Hz to 2.0 MHz). The composite film showed maximum dielectric constant of 35.77, at 200 Hz for 1.2 M concentration of nickel ion-doped mullite sintered at 1400°C, compared to 9.10, for the pure polymer. Furthermore, both dielectric constant and electrical conductivity of the composite were also highly dependent upon dopant concentration inside filler and frequency of the AC field. The AC conductivity of the developed composite increased with an increase in temperature by following Jonscher's power law, while the electrical resistivity reduced accordingly. Field emission scanning electron microscope (FESEM) characterization study showed the uniform distribution of doped mullite embedded inside the polymer matrix. Moreover, the results reflected that this novel composite material is able to follow the galloping pace of development of the smaller electronic devices, which are highly indebted to the development of very small size (microlevel/ nanolevel) as well as efficient new-generation semiconductor materials.