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^-1-10 ⁵ 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 V _O ⁺ and V _O ⁺⁺, 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.