High dielectric constant materials are of technological importance as they lead to the miniaturization of the electronic devices. In this context, the observation of anomalously high dielectric constant (>104) in the body-centered cubic perovskite-related (Space group Im3) material Calcium Copper Titanate ((CaCu3Ti4O12)(CCTO)) over wide frequency (100 Hz – 1MHz at RT) and temperature (100 – 600 K at 1 kHz ) ranges has attracted a great deal of attention. However, high dielectric constant in CCTO is not well understood yet, though internal barrier layer capacitor (IBLC) mechanism is widely been accepted. Therefore, the present work has been focused on the preparation and characterization of CCTO ceramic and to have an insight into the origin of high dielectric constant. Influence of calcination temperature, processing conditions, microstructure (and hence grain size), composition, doping etc on the electrical characteristics of CCTO ceramics were investigated. Electrical properties were found to be strongly dependent on these parameters. The dielectric constant in CCTO was observed to be reduced considerably on substituting La+3 on Ca+2 site. The formation temperature of CCTO was lowered substantially (when compared to conventional solid-state reaction route) by adopting molten-salt synthesis. The dielectric loss in CCTO was reduced by incorporating glassy phases at the grain boundary. Potential candidates for the practical applications such as charge storage devices, capacitors etc, with dielectric constant as high as 700 at 300 K was accomplished in a three-phase percolative composite fabricated by incorporating Aluminium particle into CCTO-epoxy composite. Polycrystalline CCTO thin films with dielectric constant as high as ~ 5000 (1 kHz and 400 K) were fabricated on Pt(111)/Ti/SiO2/Si substrates using radio frequency magnetron sputtering. Effect of sintering conditions on the microstructural, ferroelectric and varistor properties of CCTO and LCTO ceramics belonging to the high and low dielectric constant members of ACu3M4O12 family of oxides were investigated in detail and are compared. Ferroelectric-like hysteresis loop (P vs E) and weak pyroelectricity were observed in CCTO and plausible mechanisms for this unusual phenomenon have been proposed.

High dielectric constant materials are of technological importance as they lead to the miniaturization of the electronic devices. For instance, in the case of memory devices based on capacitive components, such as static and dynamic random access memories, the dielectric constant will ultimately decide the level of miniaturization. In this context, the observation of anomalously high dielectric constant (>10) in the double perovskite Sr2SbMnO6 (SSM) over wide frequency (100 Hz1 MHz) and (190373 K) temperature range has attracted a great deal of attention. However, unfortunately their dielectric losses were also high which limit their use for possible capacitor and related applications. The dielectric loss however was known to decrease with decreasing crystallite size in electroceramics. Therefore, the present work has been focused on the synthesis of nanocrystalline SSM powders by moltensalt route. The characterization of the ceramics fabricated from these powders for their microstructural and dielectric properties. A cubic phase of SSM powder was obtained by calcining the as synthesized powders at 900°C/10h by using sulphate flux. The crystallite size was ~ 60 nm. The activation energy associated with the particle growth was found to be 95 ± 5 kJmol-1 . The ceramic sintered at 1075°C/16h exhibited high dielectric constant (>10at 1 kHz) with low loss (0.72 at 1 kHz) at room temperature. The results are interpreted in terms of a twolayer model with conducting grains partitioned from each other by poorly conducting grain boundaries. Using this model, we attributed the two electrical responses in impedance and modulus formalisms to the grain and grain boundary effects, respectively, while the detected Debyelike relaxation and large dielectric constant were explained in terms of MaxwellWagner relaxation.

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