Enhancing the Reliability of Dy-doped BaTiO₃ Ceramics via Grain Boundary Defect Engineering

As a highly reliable dielectric material, the study of BaTiO₃ ceramic grain boundary defects is very important for the reliability of multilayer ceramic capacitors (MLCC). In this paper, a series of amphoteric rare earth element Dy-doped BaTiO₃ ceramics (Dy: 0.2, 0.5, 1.0, 2.0, and 5.0 mol%) were prepared by the solid-phase method, and the effects of the defect types induced by the differences in the doping sites of the rare earth element Dy on the crystal-boundary defect of BaTiO₃ ceramics were investigated. The results indicate that ceramic doped with 0.2 mol% Dy₂O₃ exhibit a grain size of 330 nm, conductivity activation energy of 1.534 eV, grain boundary barrier of 0.4645 eV, bandgap of 3.193 eV, and oxygen vacancy concentration of 32.67 %. Notably, this composition demonstrates higher grain boundary activation energy and barrier potential among the investigated systems. The enhanced insulating properties of grain boundaries align with the stringent requirements for high-reliability dielectric materials. The defect analysis reveals that when Dy³⁺ doping is below 1.0 mol%, Dy³⁺ substitutes Ti⁴⁺ ions to form acceptor doping, generating oxygen vacancies as donor states. This increases carrier concentration within the system, reduces grain boundary activation energy and barrier potential, consequently diminishing impedance capability. In contrast, at Dy³⁺ concentrations exceeding 1.0 mol%, partial Dy³⁺ replaces Ba²⁺ to form donor doping, inducing barium vacancies due to charge compensation. These vacancies trap electrons, enhance effective acceptor states, and elevate grain boundary activation energy and barrier potential. This study demonstrates the significant role of grain boundary defects in the grain boundary barriers of rare earth doped BaTiO₃ ceramics, providing a way to achieve high reliability of BaTiO₃-based MLCCs.