Synergistic enhancement of dielectric properties and reliability of BaTiO₃-based MLCC via compositional gradient design and nano-domain engineering

Dielectrics with a high dielectric constant, low dielectric loss, and good temperature stability are essential for barium titanate (BaTiO₃)-based multilayer ceramic capacitors (MLCCs) to meet the escalating demands of 5G communication technologies. However, challenges remain in further optimizing dielectric properties due to the correlation between these parameters. This study proposes a synergistic design strategy that overcomes this limitation through the coupling of compositional gradient control and nano-domain engineering. An optimized 900 °C pre-sintering process enables precise structural regulation, forming a tetragonal barium titanate core surrounded by a dopant-enriched graded compositional-gradient shell structure. Atomic-scale analysis confirms that the gradient design achieves directional distribution of Y/Mg/Mn dopants, stabilizes the highly tetragonal core, and confines oxygen vacancy-related defects to the shell region. This defect-localization effect suppresses long-range vacancy migration, thereby significantly enhancing insulation resistance and breakdown strength. Concurrently, the formation of relaxor-like polar nano-domains not only contributes to a high dielectric constant but also optimizes the temperature stability of the dielectric constant. Ultimately, the prepared ceramic materials exhibit a high dielectric constant (ε_r > 2200), excellent thermal stability meeting the X8R standards (ΔC/C_25°C ≤ ±15% over the temperature range of −55–150 °C, where ΔC/C_25°C is the capacitance variation) and enhanced breakdown strength (> 6.7 kV/mm). This finding implies that the synergistic regulation of compositional gradients and nano-domain engineering may be a promising strategy for designing dielectric materials with both high capacitance and robust reliability and provides a broad opportunity for the development of other dielectric materials.