Effects of bismuth on structural and dielectric properties of cobalt-cadmium spinel ferrites fabricated via micro-emulsion route

Abstract

Spinel ferrites have a significant role in high-tech applications. In the present work nano-crystalline ferrites having general formula Co0.5Cd0.5Bi x Fe2−x O4 with (x = 0.0, 0.05, 0.1, 0.15, 0.2, and 0.25) are synthesized via micro-emulsion route. Powder x-ray diffraction (XRD) studies discover the FCC spinel structure. Crystalline size is calculated in a range of 11 nm–15 nm. Lattice parameter calculations are reduced due to its substitution which leads to the exchange of large ionic radius of Fe3+ for small ionic radius of Bi3+. The x-ray density is analyzed to increase with doping. Fourier transform infrared spectroscopy (FTIR) is performed to analyze absorption band spectra. The two absorption bands are observed in a range of 400 cm−1–600 cm−1, and they are the characteristic feature of spinel structure. Thermo-gravimetric analysis (TGA) reveals the total weight loss of nearly 1.98%. Dielectric analysis is carried out by impedance analyzer in a frequency span from 1 MHz to 3 GHz by using the Maxwell Wagner model. Dielectric studies reveal the decrease of dielectric parameters. The alternating current (AC) conductivity exhibits a plane behavior in a low frequency range and it increases with the applied frequency increasing. This is attributed to the grain effects in a high frequency range or may be due to the reduction of porosity. Real and imaginary part of impedance show the decreasing trend which corresponds to the grain boundary action. The imaginary modulus shows the occurrence of peak that helps to understand the interfacial polarization. Cole-Cole graph shows a single semicircle which confirms that the conduction mechanism is due to the grain boundaries at low frequency. Dielectric studies reveal the applicability of these ferrites in high frequency equipment, microwave applications, high storage media, and semiconductor devices.