Effect of Processing on the Sintering of High Dielectric constant CaCu3Ti4O12 Ceramics

In this work, two series of ceramic CaCu3Ti4O12 (CCTO) have been prepared by a solid-state reaction, studying the effect of an extra calcination and milling step of the raw materials in one of the products. The comparison of the green powder characteristics, microstructure, and electrical properties of the sintered materials is presented and discussed. The double calcination route diminishes the amount of unreacted CuO, and thus, a thinner secondary phase <= 10 nm is better distributed among the grain boundaries enhancing the giant dielectric response. Raman spectroscopy confirms the reduction of unreacted copper, indicating the relation of the Ag (1)/Ag (2) vibrational modes that the stoichiometry of the precursors approaches that of the ideal ceramic CCTO.