Effect of the pyrochlore (Y₂Ti₂O₇) phase on the resistance degradation in yttrium-doped BaTiO₃ ceramic capacitors

Degradation of insulation resistance due to the formation of the Y₂Ti₂O₇ (pyrochlore) phases in yttrium(Y)-doped BaTiO₃ ceramics was investigated. The addition of Y₂O₃ and sintering aid SiO₂ to the BaTiO₃ ceramics caused the formation of barium-related BaSiO₃ and titanium-related Y₂Ti₂O₇ second phases. The appearance of the abnormally grown large pyrochlore grains with the increase of sintering temperature critically degraded insulation resistance at high temperatures. When the volume fraction of the pyrochlore phase increased, the resistance degradation was also observed although the grain size of the pyrochlore phase became smaller. The highly oxygen ionic conductive nature of the Y₂Ti₂O₇ pyrochlore phase is supposed to accelerate electromigration of oxygen vacancies resulting in the resistance degradation. The formation of pyrochlore phase should be prevented to guarantee the high-temperature reliability of BaTiO₃ bases ceramic capacitors.