Influence of atmospheres on the dielectric properties of calcium copper titanate ceramics

Calcium Copper Titanate Ceramics (CaCu3Ti4O12; CCTO) are useful as capacitors because of the large dielectric constant. This study investigated the effect of testing atmospheres such as air and dry N-2 on the stability and reproducibility of the electrical properties displayed by CCTO ceramics. Solid-state reaction method is used to synthesize phase pure CCTO powders, which are used to fabricate dense samples by sintering. Samples with different microstructures are obtained by sintering at different temperatures of 1070 and 1100 degrees C. AC impedance spectroscopy is used to study the effects of testing atmospheres, temperatures, microstructures, and frequency on the dielectric properties of the sintered samples. Highly irreproducible dielectric properties are observed upon testing in ambient conditions. Stable and reproducible dielectric properties are only obtained in dry N-2. Re-exposing the same CCTO samples back into ambient air after treating in dry N-2 restored irreproducibility. The results from this study suggested that the role of moisture/air in the ambient on the dielectric properties should not be over-looked and is expected to play a key role in controlling the stability of dielectric properties of CCTO. This new approach of characterizing the CCTO ceramics can be used as guidelines to eliminate hysteresis due to ambient atmosphere and to produce stable and reproducible dielectric properties useful as capacitors.