CaCu3Ti4O12 (CCTO) ceramics were fabricated by a conventional solid-state reaction at various calcination and sintering temperatures. Depending on the relative dielectric constant (epsilon(r)) at 1 kHz, the specimens can be categorized into three types: type A (epsilon(r) < 5 x 10(4)), type B (5 x 10(4) < epsilon(r) <10(5)) and type C (epsilon(r) > 10(5)). The value of epsilon(r) is closely related to the microstructure: type-A specimens show a morphology with large grains embedded in a small-grained matrix, type-B specimens present a network structure and type-C specimens display a core-shell structure. Different dielectric loss variation tendencies are observed in the type-A specimens, which can be well explained by impedance spectroscopy analysis and further confirmed by the EDX results. Also, the proper calcination and sintering temperature ranges needed to achieve good comprehensive properties are given.

Keywords: Ceramics; Dielectric properties; Microstructure