Investigating the sintering temperature and slurry tape formulation to prepare doped BaTi₄O₉ ceramic substrates with good dielectric properties

In microwave electronic applications, the advancement of resonators, filters, substrates, and waveguide circuits is significantly influenced by the dielectric ceramics. This research focuses on preparing Nb-doped BaTi₄O₉ (BT-N) dielectric ceramics, with a specific emphasis on the dielectric and mechanical properties of the BT-N tape-cast substrates. Herein, we adopted conventional solid-state sintering techniques to fabricate the BT-N ceramics and optimized the tape casting process. The slip composition was meticulously adjusted to ensure the green tapes with a smooth surface finish and robust mechanical properties, which shows high tensile strength of 0.81 MPa. The investigation results demonstrate that excessive sintering temperatures or soaking times lead to the emergence of the Ba₂Ti₉O₂₀ secondary phase, thereby adversely impacting the material’s properties. The sintering kinetics of the BT-N substrates result demonstrates that the sintering temperature of 1260 °C for a duration of 2.5 h resulted in the most favorable combination of high density and superior dielectric characteristics. The sample using tape casting lamination process exhibits a high bulk density of 4.52 g/cm³, accompanied by a dielectric constant (ε_r) of 40.38 and dielectric loss (tanδ) of 8.99 × 10^–4. Under the tape casting processing, the dielectric properties of the BT-N ceramic substrates are significantly optimized.