Dielectric properties of CaCu3Ti4O12 ceramics: effect of high purity nanometric powders

The dielectric properties of CaCu3Ti4O12 ceramics fabricated with nano-size fine powders (~30 nm) are compared with that fabricated with micro-size coarse powders (0.1–0.3 μm). For the same sintering conditions, the ceramic samples with nano-size fine powders have more uniform and denser microstructures and higher room temperature dielectric constant (~105, in the frequency range of 10−1–105 Hz) than that with micro-size coarse powders. That the use of nano powders facilitates the formation of Cu-rich amorphous phase in the grain boundary led to an increasing dielectric loss in low frequency range. Besides the common intrinsic defect structure of VO+ and VO++, the energy level of ~0.72 eV detected in high temperature range is attributed to the conduction relaxations, and the energy level of 0.30–0.40 eV which is only detected in the sample synthesized by common submicron powders is suggested to originate from the defect level of grain boundary related to Cu ions. This research provides a technical guidance for the application of this material.