P‐N Junction‐Driven Abnormal Electric Field Distribution in the Degraded Multilayer Ceramic Capacitors

Local electric field distribution in the dielectric layer of BaTiO3‐based multilayer ceramic capacitors (MLCCs) is investigated by Kelvin probe force microscopy before and after highly accelerated life test (HALT) degradation combined with the energy band diagram. An unusual electric field concentration phenomenon is directly visualized near the HALT cathode region in the degraded MLCCs while a reverse voltage is applied. Such abnormal behavior is ascribed to the migration of oxygen vacancies within the dielectric layer during the HALT, leading to the formation of a P‐N junction structure and further a heightened barrier under a reverse bias. As a result, a P‐N junctional model is proposed for understanding local failure mechanism of the degraded MLCCs, which enrich the insights into the insulation resistance degradation and the reliability of MLCCs.