Synthesis of Al2TiO5 and its effect on the properties of chitosan–NH4SCN polymer electrolytes

Abstract

In this paper, Al2TiO5 ceramic material has been synthesised and used as filler in polymer electrolyte system to enhance the conductivity. The precursor sintered at 1,050 °C and contained 0.08 mole of aluminium nitrate gives the best and complete formation of Al2TiO5. Composite polymer electrolytes of chitosan–NH4SCN containing different amount of home-made Al2TiO5 were prepared by solution casting. The addition of filler has enhanced the conductivity of polymer electrolyte. The sample 57 wt% chitosan–38 wt% NH4SCN–5 wt% Al2TiO5 exhibited the highest electrical conductivity of 2.10 × 10−4 S cm−1 at room temperature. The presence of the Al2TiO5 creates favourable pathways for ionic conduction through Lewis acid–base type interactions between ionic species and O/OH surface groups on alumina filler grains. In addition, the space charge region created by the presence of Al3+ could attract SCN−1 ions, thus immobilise it and increase the transport number of the cation. Degree of crystallinity is calculated from the deconvoluted X-ray diffraction patterns and it shows that the lowest degree of crystallinity is achieved when 5 wt% of filler is added. In Fourier transform infrared study, the carboxamide band of the polymer is observed to shift to higher wave number from 1,629 to 1,634 cm−1, confirming the formation of chitosan–NH4SCN–Al2TiO5 complexes. The morphology of composite polymer electrolyte has been studied using scanning electron microscopy at room temperature.