Effect of sintering conditions on microstructure and dielectric properties of CaCu3Ti4O12 (CCTO) ceramics

Abstract

The influence of sintering temperature and dwell time on the microstructure formation and dielectric properties of CaCu_(3)Ti_(4)O_(12) ceramics was investigated. For sintering temperatures of 1050 and 1100 °C significant differences in the CaCu_(3)Ti_(4)O_(12) ceramic microstructure and the segregation of a CuO_(x)-rich phase towards the grain boundary (GB) areas were observed with increasing dwell time. In addition to the formation of a semiconducting bulk and insulating grain boundary phase the segregated CuO_(x) forms an intergranular phase, and the effects of this phase on the dielectric properties are rather intriguing. At sintering temperature below 1050 °C only small amounts of CuO_(x) segregate, whereas sintering above 1050 °C (e.g., 1100 °C) leads to increased evaporation of the CuO_(x). Therefore, the effects of the CuOx-rich intergranular phase upon the dielectric properties are felt strongest in samples sintered at 1050 °C. Such effects are discussed in terms of microstructural variations due to liquid phase sintering behavior facilitated by the TiO_(2)-CuO_(x)-eutectic, which appearsto be melted at high sintering temperature prior to evaporation of CuO_(x) at prolonged dwell times at the highest sintering temperatures(1100 °C).