Synergistic grain and interface engineering of nano-BaTiO3 ceramics for ultra-thin MLCCs with high reliability

Ultra-thin multilayer ceramic capacitors (MLCCs) require nano-sized BaTiO 3 -based ceramics with simultaneously high dielectric performance and reliability, while abnormal grain growth in conventional solid-state processing severely limits further miniaturization. Herein, a synergistic grain and interface engineering integrating pre-coating with two-step sintering is proposed to precisely regulate grain growth and microstructural evolution. As a result, ultrafine-grained BaTiO 3 -based ceramics with a uniform core-shell structure were achieved, exhibiting an average grain size of (131 ± 53) nm, a high relative density of 97.76%, and complete suppression of abnormal grain growth. The optimized ceramics fully satisfy the EIA-X7S specification (ΔC/C 25℃ = ±22%, −55–125 ℃), delivering a dielectric constant of 2177 and a dielectric loss below 0.01 at 25 ℃. Mechanistic investigations reveal that Mg pre-coating regulates elemental diffusion effectively and promotes defect dipole formation 2 Ho Ba · − Mg Ti ′ ′ $\left[{2\mathit{Ho}}_{\mathit{Ba}}^{\text{·}}-{\mathit{Mg}}_{\mathit{Ti}}^{\prime \prime }\right]$ , thereby confining charge carriers and enhancing electrical stability. Consequently, the corresponding ultra-thin MLCCs exhibit a high breakdown field strength of up to 95 V/μm, demonstrating markedly improved reliability. This work offers a practical and scalable materials design strategy for next-generation ultra-thin MLCCs with high performance.