Jianying Li
Xi’an Jiaotong University, China
Title: Enhanced breakdown field in CaCu3Ti4O12 ceramics: Effect of in-situ secondary phase
Biography
Biography: Jianying Li
Abstract
The electric breakdown field of CaCu3Ti4O12 (CCTO) ceramics has been enhanced by one order, i.e. from the conventional 1.0-2.0 kV/cm to 21kV/cm. Such great enhancement, associated with lower and relatively flat dielectric loss at low frequency, was arisen from a secondary phase of CuAl2O4, which was introduced by dispersion-precipitation of Al2O3 around CCTO powders and optimized sintering process. As comparisons, CuAl2O4 powder was also directly added to prepare CCTO-CuAl2O4 composite ceramics. For both in-situ and direct methods, the highest breakdown fields can be found in the samples sintered at 1100oC for 4 h with 50 mol% CuAl2O4, while the direct sample exhibited lower breakdown field than in-situ sample. It is indicated that this enchantment can be attributed to both the blocking effect of secondary phase and consumption of Cu-rich phase of in-situ reaction to avoid abnormal growth during sintering. The performance of grain boundary can be described well by the Schottky barrier model. It is found that the activation energy of hopping conduction at grain boundary is increased from 0.60 eV to 0.81 eV due to the secondary phase, which consequently leads to enhanced breakdown field.