Development of bismuth-based electronic materials from Indian red mud

This paper reports the synthesis and characterization of bismuth-based new electronic materials fabricated from silicon-free Indian red mud (RM). The materials were prepared using a solid-state reaction technique. Preliminary X-ray (XRD) structural analysis exhibits the formation of compounds closely related to BiFeO3 (with the presence of some additional impurity phases). The surface morphology recorded by scanning electron microscopy (SEM) reveals a polycrystalline nature of texture with uniform distribution of grains. Some dielectric parameters (relative permittivity (εr) and tangent loss (tanδ)) of the compounds are almost independent on frequency in the low-temperature range. In the high- temperature region, relative permittivity of the compounds is found to be higher with low tangent loss. Detailed studies of impedance and related parameters exhibit that the parameters are strongly dependent on temperature, and show a good correlation with their microstructures. The bulk resistance, evaluated from complex impedance spectra, is found to be decreasing with rise in temperature. The nature of impedance spectra exhibits a typical negative-temperature-co-efficient of resistance (NTCR) behavior similar to the semiconductors. Studies of electric modulus show the presence of hopping conduction mechanism in the system with non-exponential type of conduction relaxation. The low-leakage current and NTCR behavior of the materials are found to be consistent with their J-E characteristics. The ac conductivity spectra of the materials show a typical-signature of an ionic conducting system, and are found to obey Jonscher׳s universal power law.