Dielectric and grain-boundary characteristics of hot pressed CaCu ₃Ti₄O₁₂

Effects of hot pressing (HP) on the dielectric and grain-boundary characteristics of copper titanate (CaCu₃Ti₄O₁₂ or CCTO) materials were studied with the comparison of conventionally prepared samples. HP at 1100°C in N₂ atmosphere resulted in uniformly distributed smaller grain sizes and less Cu-rich grain boundaries, without the accompanying secondary CuO phase. The high effective permittivity of ∼3 × 10⁴ at 1 kHz, obtained in the HP sample having a relatively smaller grain size of ∼2.4 μm, is assumed to be associated with a higher dielectric constant of thinner grain-boundary phases. The low grain-boundary resistivities of 199-319 kΩ·cm in the HP samples are likely induced by the N₂ atmosphere and less Cu-rich grain-boundary phase.