Grain size effect on the dielectric and non-ohmic properties of CaCu3Ti4O12 ceramics prepared by the sol-gel process

Abstract

Grain size control is very important for enhancing the electric properties of CaCu3Ti4O12 (CCTO) ceramics. The effect of grain sizes on the dielectric and non-ohmic properties of the CCTO ceramics was investigated. Firstly, CCTO precursor powders were synthesized by the sol-gel process. Then the CCTO ceramics with different grain sizes were obtained under the same condition by using the powders calcined at different temperature. The XRD patterns of the sintered CCTO ceramics show the cubic perovskite with pure CCTO phases. The SEM results indicate that the mean grain sizes range of the CCTO ceramics are about 2.03(±0.66) ∼ 9.02(±3.57) μm. The electrical properties of the CCTO ceramics demonstrate that the change of the grain size obviously affects the non-ohmic characteristics and dielectric properties. And the larger grain size is beneficial to enhance the dielectric constant (ε ≈ 3 × 104, at a frequency of 1k Hz), while the smaller grain size is beneficial to improve its breakdown field (Eb ≈ 6010 V/cm) and nonlinear coefficient (α ≈ 24), which can be explained by the barrier behavior of Schottky-type model and the grain boundary properties of the internal barrier layer capacitor (IBLC) model. This work may provide an effective way to design high dielectric constant and nonlinear coefficient CCTO materials from the viewpoint of controlling grain size through the preparation parameter of the powders.