Effect of manganese and vanadium valences on microstructures and reliability of BaTiO3-based multi-layer ceramic capacitors

The valences of manganese and vanadium oxides in multi-layer ceramic capacitors (MLCCs), sintered under a reducing atmosphere, were investigated using electron paramagnetic resonance; insulation resistance degradation was analyzed using impedance spectroscopy in highly accelerated lifetime tests to clarify the influences of manganese and vanadium on both the electrical properties and microstructure of MLCCs. The Mn²⁺ was stable in the reducing-atmosphere-sintered MLCCs and formed a grain boundary. Vanadium mitigated insulation resistance degradation and increased the reliability of the MLCCs. Although V⁴⁺ was detected in MLCCs that had 0.20 mol% and 0.30 mol% of added vanadium, the electrical properties were dependent upon other ions, e.g., V³⁺ or V⁵⁺. All vanadium ions except for V⁴⁺ decreased the insulation resistance of ceramic/electrode interface. This is because vanadium reduces electric field concentration at the ceramic/electrode interface and delays the onset of oxygen vacancy migration in the early stages of a highly accelerated lifetime test.