Microstructures and Dielectric Properties of CaCu₃Ti₄O₁₂ Polycrystalline Ceramics

We report important factors affecting the dielectric properties of CaCu3Ti4O12 (CCTO) polycrystalline ceramics prepared by the conventional solid-state ceramic process. The relative dielectric constants (εr) up to several thousands (~ 3,000 at 1 kHz) were gradually increased with increasing the sintered density of samples in the case that no exaggerated grain growth occurred. An abrupt increase in εr values were, however, accompanied by the formation of abnormally grown large grains, and thus with increasing the population of abnormally grown grains, which could be achieved by a prolonged sintering at 1060°C, the εr values were remarkably increased from several thousands to ~105. Optimally processed CCTO sample exhibited a very high εr of ~ 90,000 at 1 kHz.