Microstructural Engineering of BaTiO3 Ceramics: The Synergistic Effects of Sintering Temperature and Initial Particle Size on Core–Shell Structure and Dielectric Reliability

The microstructural design of BaTiO 3 -based ceramics plays a critical role in achieving high dielectric stability and reliability for advanced multilayer ceramic capacitors (MLCCs). In this work, we systematically investigate the synergistic effects of sintering temperature and initial BaTiO 3 particle size on the formation of core–shell structures and their impact on dielectric performance. By employing commercial BaTiO 3 powders with particle sizes ranging from 100 to 250 nm and optimizing sintering conditions, a well-regulated core–shell architecture is constructed via a combination of solid solution–diffusion and dissolution–precipitation mechanisms. Microstructural and compositional analyses reveal that excessively fine powders or insufficient sintering temperatures disrupt shell formation, while moderate particle sizes and elevated sintering temperatures promote shell uniformity and dopant segregation at grain boundaries. These features result in enhanced dielectric relaxation, stabilized capacitance-temperature characteristics, and suppressed oxygen vacancy migration. The sample exhibited the optimal performance, achieving a dielectric constant of 1850, a dielectric loss of 0.017, and minimal capacitance variation, which satisfies the X8S standard. Impedance spectroscopy indicated a high activation energy for oxygen vacancy migration in grain boundaries, implying superior electrical reliability. This work offers valuable insights into the structure–property relationship of BaTiO 3 ceramics and emphasizes the role of sintering–particle size synergy in designing reliable dielectrics for advanced MLCCs.