In this study, the dielectric and electrical properties of high-capacitance base metal electrode (BME) multilayer ceramic capacitors (MLCCs) fabricated using a BaTiO₃-MgO-Mn₃O₄-(Na₀.₅Bi₀.₅)TiO₃ (NBT)-(BaCa)SiO₃ dielectric system were investigated under reducing atmospheres with oxygen partial pressures (PO₂) ranging from 10⁻1⁰ to 10⁻12 MPa. By incorporating NBT, the dielectric performance remained stable across the entire range of reducing atmospheres. The fabricated MLCCs exhibited consistent capacitance values, low dielectric loss (<2.8%), and high insulation resistance, reaching up to 2.4 GΩ at 25℃ and 0.675 GΩ at 125℃. Furthermore, excellent breakdown voltage performance (up to 550 V at 25℃) and Class II-compatible temperature coefficient of capacitance (TCC) behavior were observed, meeting the X8R specification. The BaTiO₃-MgO-Mn₃O₄-NBT-(BaCa)SiO₃ dielectric system demonstrates that NBT can serve as a promising alternative to conventional rare-earth dopants in BME MLCCs, enabling excellent thermal and electrical stability, high capacitance, and longterm reliability even under reducing conditions. These results confirm the feasibility of developing cost-effective, sustainable, and rare-earth-free MLCCs for high-performance applications in automotive, industrial, and energy storage systems.
