Influence of the processing rates and sintering temperatures on the dielectric properties of CaCu3Ti4O12 ceramics

The stoichiometric CaCu3Ti4O12 pellets were prepared by the solid state synthesis. X-ray diffraction data revealed the tenorite CuO and cuprite Cu2O secondary phases on the unpolished CaCu3Ti4O12 samples regardless of the heating rates. Also, the dielectric constant marked the highest for the CaCu3Ti4O12 sample sintered at the lowest heating rate (1A degrees C/min), which was explained by the increased grain conductivity due to the cation reactions. On the other hand, Cu2O phase was found only on the unpolished CaCu3Ti4O12 sample sintered over 1100A degrees C and those are considered as the remains reduced from the CuO phase. The higher sintering temperature showed the increased dielectric constant and the loss tangent of the CaCu3Ti4O12 samples, and this result could be interpreted by the impedance measurement data. The relationship between the processing condition and the dielectric properties was discussed in terms of the cation non-stoichiometry and the defect chemistry in CaCu3Ti4O12.