As a typical garnet transparent ceramic used in high-energy solid-state laser systems, terbium aluminum garnet (Tb₃Al₅O₁₂, TAG) magneto-optic ceramics have become a focal point of research due to their excellent magneto-optic properties and high-power performance. This paper focuses on TAG magneto-optic ceramics prepared by vacuum solid-state reaction, with particular emphasis on the optimization of sintering aids and lattice doping modifications. By comparison, the most suitable additives for TAG ceramics were identified. The study highlights the longstanding challenge in improving the quality of TAG ceramics, which arises from the reliance on large doses of sintering aids and the resulting compositional inhomogeneity caused by sintering aid residues. To address these issues, we present our latest research, which involves co-doping the lattice with Mg²⁺ and Si⁴⁺. This approach enables the preparation of higher optical quality TAG ceramics via a one-step vacuum solid-state sintering process, without reducing the absolute amount of MgO and TEOS. The best sample achieve a transmittance of 82.48% at 1 064 nm, which, to our knowledge, is the highest value reported using a similar sintering method based on domestic powders. This lattice doping strategy, rather than the traditional mass-ratio addition of sintering aids, offers a promising new approach for further improving the quality of garnet transparent ceramics used in high-energy laser systems.