Characterization, Structure, Dielectric Permittivity, and AC Conductivity of Co–Ni-Doped Bentonite at Room Temperature

Abstract

xCo–5%Ni (where x = 0, 1, 3, and 5%) coatings on bentonite were synthesized by insipient wet impregnation method. The phase structures of the coatings, surface analysis, dielectric property of the samples as a function of frequency (at room temperature), were characterized using X-ray diffractometer, energy-dispersive X-ray spectroscopy (EDX) and analytical response analyzer, respectively. The EDX confirmed the presence of Ni and Co in proportions qualitatively consistent with the concentrations of the synthesized composites. X-ray diffraction measurement confirmed the presence of montmorillonite and quartz as the main components in bentonite. Peaks shift has been noticed toward lower diffraction angle in bentonite X-ray diffractogram after insertion of metal ions (Ni and Co ions) which might be due to lattice expansion. The lattice constant was found to be 4.35, 4.42, and 4.41 A for 1%Co–5%Ni/bentonite, 3%Co–5%Ni/bentonite and 5%Co–5%Ni/bentonite, respectively. The diffraction peak at 37.2°, observed for all composites, was ascribed to (111) plane of the NiO cubic phase. The crystallite size has been calculated by Scherer formula and was found to increase from 3.19 to 8.43 nm with increasing the wt% of Co. The dielectric permittivity has decreased with increasing frequency and further decreased by doping. The value of AC conductivity has increased with an increase in frequency. The conduction mechanism for doped samples was hopping, while that for bentonite was due to the localized/reorientation processes.