Crystal structure refinement, optical properties, dielectric response, and impedance spectroscopy of Ni2+-Co2+ substituted bismuth copper titanate (BCTO)

We have synthesized single phase Ni+2-Co+2 substituted bismuth copper titanate (Bi2/3Cu3Ti4O12) electroceramic using the sol-gel autocombustion method. The XRD patterns reveal that the prepared BCTO electroceramic are of single phase without the presence of any other phases such as CuO or TiO2. FESEM micrographs show particles with well-defined cubic shape of bismuth copper titanate ceramics. EDX spectra shows all the chemical elements of the prepared composition, this confirm the stoichiometry and the purity of the synthesized electroceramic. The optical band gap study was carried out using UV-Vis-NIR spectroscopy in the region 225-1000 nm and the highest value of 3.63 eV was observed in the sample having x = 0.1. The dielectric response and impedance spectroscopy of the electroceramic were discussed based on Debye-type relaxation process and Maxwell-Wagner model. The sample having x = 0.0 shows the highest dielectric constant (3800) at room-temperature and a frequency of 42 Hz as compared to x = 0.1 and x = 0.2. The Cole-Cole plots of complex impedance and complex electric modulus indicate that grain-boundary resistance is the major contributor to the dielectric response of the prepared BCTO electroceramic.