The re‐oxidation process is an important thermal processing step to minimize oxygen vacancies and to produce a high resistivity and more reliable multilayer ceramic capacitors (MLCC) upon co‐firing with Ni internal electrodes. A model X7R capacitor based on Ho2O3 amphoteric doping is investigated in prototyped multilayer devices. The dielectrics are co‐fired in a standard low pO2 sintering process. The re‐oxidation thermal process of these multilayer devices is then investigated with a series of “in‐situ” impedance measurements. These measurements are performed in a temperature range from 400° to 500°C in air. The relative impedance change is used to determine effective chemical diffusion coefficients and associated activation energy. The electrical conductivity is analyzed to determine properties, such as Schottky barrier height and degradation lifetime, under different re‐oxidation conditions. Furthermore, transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) are applied to consider the microstructure, microchemistry, and oxygen stoichiometry changes.

Over the past decade, multilayer ceramic capacitors (MLCCs) have been able to achieve very high volumetric capacitance due to continuous improvement in their process technology. However, the performance of these devices is severely limited by the presence of electrode defects such as electrode porosity and roughness. To assess the effect of microstructure on MLCC performance, two sets of multilayer capacitors subjected to different processing conditions are compared for their microstructure and electrical properties. It is shown that more continuous and planar electrode morphology leads to lower local electric fields and thus, superior performance. These computational predictions are verified using electrical property measurements. Capacitors with higher electrode continuity exhibit proportionally higher capacitance, provided the grain‐size distributions are similar. From the leakage current measurements, it is found that the Schottky barrier at the electrode–dielectric interface controls the conduction mechanism. This barrier height is adversely affected by the microstructural defects such as electrode discontinuities and roughness. These results are further supported by frequency‐dependent impedance measurements.

Re-oxidation is an important thermal process to minimize oxygen vacancies and produce high reliable Ni-MLCCs. The re-oxidation of these devices is then investigated with a series of “in-situ” impedance measurements between 400 and 500 °C in air. From the relative impedance change, chemical diffusion coefficients, associated activation energy and effective equivalent circuit model are determined. Those values were found to be reasonable compared with previous researchers’ data. Moreover, the proposed effective equivalent circuit model successfully represents the real Ni-MLCC morphology. From transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS), it is found that the electrical properties and reliabilities of the Ni-MLCCs re-oxidized under different conditions are identical.