Spatial distribution of oxygen vacancies in BaTiO ₃ ‐based multilayer ceramic capacitors via cathodoluminescence

Abstract The insulation resistance (IR) degradation of BaTiO 3 ‐based multilayer ceramic capacitors (MLCCs) is predominantly attributed to the migration and accumulation of oxygen vacancies () toward the cathode. This study innovatively investigates the spatial distribution characteristics of using cathodoluminescence (CL) spectroscopy. The physical mechanism of CL emission primarily involves the recombination of electrons and holes between defect energy levels, such as those associated with , barium vacancies (), and Ti 3+ , and the valence and conduction bands. CL test results indicated that the , , and Ti 3+ concentration progressively increased from the central region of the MLCCs toward the electrode edges, and further to the external ceramic layer. Destructive physical analysis and computed tomography were performed on MLCCs that experienced breakdown failure after IR degradation. The analysis revealed that over 90% of the failure initiation sites were located at the electrode edges, indicating that a high concentration promotes failure occurrence. Furthermore, the combined effect of localized electric field concentration and the propensity for heat accumulation also plays a critical role, making the electrode edge along the W‐direction the most susceptible site for failure initiation. This study provides a theoretical foundation for a comprehensive understanding of the IR degradation behavior in MLCCs.