Li₂CO₃-coated Ni particles for the inner electrodes of multilayer ceramic capacitors: Evaluation of lifetime

In previous work, it was demonstrated that using Li₂CO₃-coated Ni particles in the manufacturing of multilayer ceramic capacitor (MLCC) devices could improve both the permittivity and dissipation factors. However, adding Li⁺ ions to the system gave rise to the concern that ions could migrate under sustained electrical fields and thereby increase the degradation rates of the insulation resistance in MLCCs. In this paper, thermally stimulated depolarization current and highly accelerated lifetime testing were both utilized to evaluate the oxygen vacancy space-charge regions and migration in MLCCs. The results suggested that three parameters (the sintering schedule, Li₂CO₃ coatings, and oxygen flow during sintering) determine the overall resilience to the degradation. The Li⁺ ions did not migrate during degradation, as verified by time-of-flight secondary-ion mass spectrometry mapping; however, the Li ions enter the perovskite structure as an acceptor and, if ionically compensated for, could introduce more oxygen vacancies to the system and decrease the lifetime of the MLCCs. Nevertheless, it was demonstrated that the relative lifetimes of the newly designed MLCCs significantly improve relative to the conventional samples.