Synergetic engineering of SrO vacancies and core-rim interfacial structures in dielectric Sr1-xBaxTiO3 ceramics

High dielectric constant can be reached in a reductive-sintered Sr1-xBaxTiO3 barrier-layer capacitor with core-rim structures as dominant microstructural features. By SEM and aberration-corrected TEM observations, an interfacial zone between the core and rim, named as white-rim (w-rim), was found always enriched with Ba, while the core was free of Ba solution. The reductive liquid-phase sintering resulted in three times the concentrations of oxygen vacancies (V-O) into cores and rims compared to their A-site vacancies (V-A), while enabling the highest concentration of V-O (similar to 17%) without V-A in w-rim. The strained core/w-rim interfaces, with obvious interfacial polarizations, which can effectively raise the dielectric constant, were expected to be created from a temporary equilibrium between the cores and the liquid-phase. The synergetic evolution of core-rim structures, Sr-O vacancies, multiple internal polarized structures can be utilized to better control and optimize dielectric behaviors and other functionalities for perovskite capacitors and other multi-functional ceramics.