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The discovery of innovative multifunctional ceramics is an important topic in the recent field of research and development. Perovskite oxide ceramics exhibit a wide range of multifunctional characteristics, such as ferromagnetism, ferro-, piezo-, and pyro-electricity and nonlinear dielectric properties. These characteristics are significant for use in environmental remediation, sensors, filters, energy conversion, and storage, corrosion-resistance coatings, aerospace industries, separators, detectors, antennas, etc. The calcium copper titanate (CCTO) with colossal dielectric constant with low dielectric loss tangent, and its isomorphs have piqued the interest of the development of advanced capacitor materials for electronic industries. CaCu3Ti4O12 (CCTO) exhibits the most extraordinary characteristic, with a dielectric permittivity at 1 kHz of ~ 104 that is essentially constant from ambient temperature to 300 °C. The substitution of metal cations/anions is an effective strategy to enhance the properties of the CCTO ceramics and extend their applications. In this review, we systematically examined the advancements of CCTO ceramics, including their structural morphology, tolerance factor, extrinsic/intrinsic mechanisms, different synthesis techniques, sintering techniques, and the effect of single doping as well as the co-doping mechanism for the enhancement of the dielectric and electrical properties. A series of CCTO-based ceramics have been summarized and explained their mechanisms and electrical properties. We anticipate that our study will help as an overview and motivate other researchers to continue working on the fabrication of CCTO or other electro-ceramics in the upcoming years. [ABSTRACT FROM AUTHOR]

CaCu3Ti4O12 (CCTO) electro ceramic was prepared by a solid-state reaction technique. The formation of CCTO was confirmed by X-ray diffraction (XRD). Pellets of calcined powder were sintered at different temperatures for two different durations, i.e., 2 and 10 h (h). The morphology and grain size of the samples were observed using scanning electron microscopy (SEM). SEM images showed that the minor phase (CuO) plays an important role in the growth of grain size. It seems that higher sintering temperatures led to change in the oxidation states of Cu and Ti, which increase the volume fraction of the CuO minor phase. Dielectric studies show that the dielectric constant is increasing with increasing sintering temperature, holding time, and presence of the CuO phase. The highest dielectric constant of ~ 41,000 was observed for CCTO samples sintered at 1100 °C for 10 h. The present samples find application in the energy storage devices. [ABSTRACT FROM AUTHOR]

The nanocrystals of CaCu3Ti4O12 ceramic were prepared by microwave flash combustion technique. The microwave sintering of powders was optimized to 1025 − 1075 °C for 20 min with heating and cooling rate of 50 °C/min. Microstructural evaluation of sintered sample was carried out using SEM. The dielectric properties were measured in the frequency range 10–2 × 106 Hz and the temperature range 30–100 °C. The CCTO sample sintered at 1075 °C had giant dielectric constant 53,300 at 100 Hz. It was observed that dielectric constant was greatly increased on a slight increase in sintering temperature. Modulus and impedance analysis were performed to explore the observed unusual dielectric response. Grain and grain boundary resistance were observed as 8 Ω and 350,000 Ω, respectively. The grain boundary activation energy for electro-conduction was calculated as 0.65 eV by using the characteristic frequencies in cole-cole plots. It was noticed that the thermally activated charge carriers had long-range mobility. [ABSTRACT FROM AUTHOR]