Achieving X8R specifications and enhanced anti-reduction in fine-grained BaTiO3: The multiple roles of chemical coating erbium

To address the demand for high-performance automotive electronics, this study develops Er 3+ -modified BaTiO 3 -based ceramics with a higher upper operating temperature (>125 °C), fine-grain, and anti-reduction properties for base metal electrode (BME) multilayer ceramic capacitors (MLCCs) utilizing a chemical coating process. The addition of Er 3+ inhibits grain growth, promotes phase transition and hinders oxygen vacancy migration, significantly enhancing the temperature stability and insulation resistivity under a reducing atmosphere. At an optimal coated level of 0.03 mol, the ceramic achieves a fine-grain (195 nm) microstructure and meets the EIA X8R specifications (−55 °C to 150 °C, ΔC/C 25°C  ≤ ±15%). The material demonstrates excellent properties, including a high dielectric constant (ε r  ∼ 1705), low dielectric loss (tanδ ∼ 0.0054), and competitive insulation resistivity (ρ v  ∼ 3.37 × 10 12  Ω cm). These findings provide theoretical guidance for developing temperature-stable BME MLCCs with a single-layer thickness of only 1 μm or even less.