<p>Bi_2-2x/3Sr_xCu₃Ti₄O₁₂ ceramics were synthesized by the conventional solid-state reaction method, and the synergistic effects of Sr²⁺ doping with ordinary and buried sintering processes on microstructure, defect formation, and dielectric properties were systematically investigated. All sintered ceramics show the pure cubic perovskite-related structure, with the buried sintered ceramic showing higher relative densities. The buried sintering process can inhibit the volatilization of Bi₂O₃ and enhance the Sr²⁺ doping efficiency, significantly reducing defect levels, primarily by decreasing A-site vacancies, which in turn inhibit the reduction of Cu²⁺ to Cu⁺ and the formation of oxygen vacancies. Sr²⁺ doping increased the dielectric constant, while the dielectric loss declined. Compared to ordinary sintering, buried sintered samples exhibited higher dielectric constants. The combined effects of doping and sintering influenced the electrical behavior of grains, grain boundaries, and electrode interfaces. Highly doped buried sintered ceramics exhibited pronounced low-frequency electrode polarization, and the dielectric constant at mid-frequency originated from the contribution of internal barrier layer capacitors (IBLC).</p>