Analysis of Mechanism of Improvement in Highly Accelerated Lifetime via Measurement of Vanadium Valence in Multilayer Ceramic Capacitors

The valence of vanadium was measured by electron paramagnetic resonance in order to explain the decrease in insulation resistance (IR) and the improvement in highly accelerated lifetime that resulted from the addition of vanadium. V4+ was detected in specimens with vanadium contents of 0.20 and 0.30 mol %, while no V4+ was detected in a specimen with a vanadium content of 0.06 mol %. It was also revealed that the content of the vanadium except for V4+ are the main factor responsible for the decrease in IR and the improvement in lifetime. The impedance of BaTiO3-based materials in multilayer ceramic capacitors with various vanadium contents was investigated in order to determine the mechanism of improving the highly accelerated lifetime using a four resistance and capacitor section electrical equivalent circuit. All four resistance components (R components) decreased with an increase in vanadium content. During the lifetime test, all four R components were degraded. In particular, the R component corresponding to the ceramic/internal electrode interface regions was more strongly degraded than the other three R components, and it was found that this component was the main factor responsible for the degradation of IR during the test. The resistance degradation of this component tended to occur slowly when the vanadium content increased, which resulted in the improvement in lifetime. The primary part of this degradation was implied to be controlled by diffusion.