Abstract: The study investigates the influence of different raw material particle sizes of barium titanate (BaTiO₃, BT) on the dielectric properties of ceramics and aims to optimize their electrical performance through doping modifications. Ceramic samples were prepared using BT powders with particle sizes of 100 nm, 150 nm, 200 nm, and 250 nm via the solid-state ball milling method. Y₂O₃, Ho₂O₃, MgO, and SiO₂ were introduced as dopants to control grain growth and tailor the dielectric properties. The microstructure and dielectric characteristics of the ceramic samples were systematically analyzed using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and dielectric measurements. The results revealed that the BT-10 sample exhibited significant dopant diffusion, which hindered the formation of an ideal “core-shell” structure and reduced tetragonality. While BT-10 showed a relatively high dielectric constant, its temperature stability was poor. In contrast, the BT-15, BT-20, and BT-25 samples successfully formed a “core-shell” structure, with BT-25 demonstrating the highest tetragonality. The BT-25 sample exhibited the most favorable electrical performance, including the highest saturation polarization strength (P_s＝11.817 μC/cm²), remanent polarization strength (P_r＝1.465 μC/cm²), and superior dielectric stability under direct current bias conditions. These findings indicate that the BT-25 sample offers the most balanced and optimized overall performance. Furthermore, the study highlights the challenges associated with using smaller BT particle sizes in fabricating “core-shell” structured ceramics, particularly the increased specific surface area and higher defect density of BT powders. This research provides valuable theoretical insights and technical guidance for optimizing the dielectric layers of multilayer ceramic capacitors.