Effects of Cu and Ti excess on the dielectric properties of CaCu3Ti4O12 prepared using a wet chemical method

The effects of Cu excess on the dielectric properties of CaCu3Ti4O12 were studied in this paper. The CaCu3Ti4O12 was synthesized starting from a solution of TiO2 sol to which appropriate amounts of Ca and Cu nitrates were added. Due to the differences in solubilities of the constituents, variations from ideal stoichiometry and a high solution pH was necessary in order to obtain final stoichiometric precipitates. Excess CuO, observed in the SEM as a separate phase surrounding the CaCu3Ti4O12 grains, were obtained by varying the parameters. Samples with a high CuO excess content showed lower dielectric constants (<10 000), compared to samples with very low CuO content (∼50 000). The higher dielectric constant of nearly pure CaCu3Ti4O12 samples could not be attributed to the volumetric content alone which implies an extrinsic factor such as the distribution of Cu rich phase at the grain boundaries.