Microstructure Optimization via Grain-Boundary Segregation to Enhance DC Bias Dielectric Performance of BaTiO₃ Multilayer Ceramic Capacitors.

Abstract

BaTiO₃-based multilayer ceramic capacitors (MLCCs) are essential components in modern electronics. To enhance overall capacitance, achieving thinner ceramic layers has become a primary issue. However, this introduces two major challenges: controlling grain size during processing and ensuring stability under high electric fields. In this study, a novel strategy employing single-element additives such as Fe³⁺ and Ni²⁺ is presented to effectively suppress grain growth. These additives strongly segregate at grain boundaries, thereby limiting grain coarsening during sintering and enabling fine-grained microstructures. The optimized BaTiO₃ samples, free of costly rare-earth elements, exhibit stable high permittivity (≈10³), low dielectric loss, and improved reliability across varying temperatures and frequencies. More importantly, we identify the ideal grain size of ≈200 nm for maximizing capacitance under a DC bias exceeding 4 V µm^-1. The findings suggest that further reducing the dielectric layer thickness to 200 nm represents a promising direction for future MLCCs.