Influence of the processing rates and sintering temperatures on the dielectric properties of CaCu^sub 3^Ti^sub 4^O^sub 12^ ceramics

The stoichiometric CaCu^sub 3^Ti^sub 4^O^sub 12^ pellets were prepared by the solid state synthesis. X-ray diffraction data revealed the tenorite CuO and cuprite Cu^sub 2^O secondary phases on the unpolished CaCu^sub 3^Ti^sub 4^O^sub 12^ samples regardless of the heating rates. Also, the dielectric constant marked the highest for the CaCu^sub 3^Ti^sub 4^O^sub 12^ sample sintered at the lowest heating rate (1°C/min), which was explained by the increased grain conductivity due to the cation reactions. On the other hand, Cu^sub 2^O phase was found only on the unpolished CaCu^sub 3^Ti^sub 4^O^sub 12^ sample sintered over 1100°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 CaCu^sub 3^Ti^sub 4^O^sub 12^ 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 CaCu^sub 3^Ti^sub 4^O^sub 12^.[PUBLICATION ABSTRACT]