MgTiO₃-based ceramics for enhanced EMI shielding solutions in K and Ka frequency bands

This study investigates the microwave dielectric and shielding properties of MgTiO₃-based solid solutions across the K (18–26.5 GHz) and Ka (26.5–40 GHz) frequency bands. Synthesized via a conventional solid-state mixed oxide route using MgO and Mg(OH)₂ as raw materials, the dielectric properties of MgTiO₃ and Mg(Ti_0.95Sn_0.05)O₃ solid solutions varied with composition and raw material. Results showed that MgO-based materials exhibited higher relative permittivity (ɛ_r) and loss tangent (tan δ) compared to Mg(OH)₂-based materials. Furthermore, the ɛ_r of the prepared samples decreased with Sn⁴⁺ substitution, attributed to the lower dielectric polarizability of Sn⁴⁺ cations compared to Ti⁴⁺ cations. Results also indicated a decrease in tan δ with Sn⁴⁺ substitution, resulting from a reduction in octahedral tilting upon partial replacement of Ti⁴⁺ cations with Sn⁴⁺ cations in MgTiO₃. Shielding property characterization revealed that all samples exhibited frequency-selective and tunable shielding capabilities, with tuning achievable through variations in composition or shield thickness. Notably, in the K frequency band, MgO-based MgTiO₃ exhibited superior dielectric properties, with a sample thickness of 2.9 mm achieving a shielding effectiveness (SE) of up to 35.62 dB at 22.30 GHz, effectively suppressing over 99.97% of incoming radiation. Similarly, in the Ka frequency band, MgO-based Mg(Ti_0.95Sn_0.05)O₃ demonstrated remarkable SE, with a sample thickness of 1.8 mm reaching SE of 38.62 dB at 31.60 GHz, attenuating over 99.98% of incoming radiation. These findings suggest potential for frequency-selective and adjustable EMI shielding in next-gen technologies.