Perovskite barium titanate (BaTiO₃) demonstrates exceptional dielectric properties as a promising microwave-absorbing (MA) material. Leveraging structural flexibility of perovskites, magnetic components can be incorporated at A/B-sites to enhance MA performance, yet the fundamental disparity in MA mechanisms between A/B-site magnetic doping remains elusive. Herein, nickel-doped BaTiO₃ perovskites were systematically synthesized through precise adjustment of the Ba/Ti molar ratio to achieve both A-site (Ni_xBa_1−xTiO₃, N_xBTO) and B-site (BaTi_1−xNi_xO₃, BTN_xO) substitutions (0 ≤ x ≤ 0.1) via a simple one-step hydrothermal method. Notably, A-site Ni²⁺ substitution in N_xBTO induced superior magnetic loss (tanδ_μ = 0.39) attributed to eddy-current dissipation, while B-site doping in BTN_xO achieved higher dielectric loss (tanδ_ε = 0.49). The N_0.1BTO sample exhibited optimal MA performance with a remarkable minimum reflection loss (RL_min) of −44.39 dB and broad effective absorption bandwidth (EAB = 8.66 GHz) covering the Ku-band and 67% X-band. Multimodal analysis revealed synergistic interactions among multiple reflection and scattering, multi-polarization relaxation, natural resonance, and eddy currents. In contrast, BTN_0.01O demonstrated deeper RL_min (−50.88 dB) but narrower EAB (3.33 GHz) governed by dielectric mechanisms. Structural characterization indicated A-site doping induced lattice distortion, reduced unit-cell volume, and optimized oxygen vacancy distribution, synergistically balancing magneto-dielectric parameters. Conversely, B-site substitution increased oxygen vacancy concentration and carrier mobility while amplifying dielectric fluctuations. The spatial occupation preference of A/B dopants (A-site and B-site) governs lattice symmetry breaking, consequently establishing structure–property relationships and underpinning the material’s tunable dielectric behavior and magnetic phenomena. This work proposes a site-selective doping strategy for designing high-performance perovskite MA materials through magneto-dielectric equilibrium optimization.

Herein, the electromagnetic shielding performance of surface concave-convex (SC) and zig-zag micro-arrays was studied by using a simulation prediction and a three-dimensional (3D) printing custom model. Firstly, surface stripe concave-convex (SSC) and surface cylindrical concave-convex (SCC) micro-arrays with or without zig-zag micro-arrays are designed, and their shielding performance is simulated in multi-bands (C-, X-band). The multiwalled carbon nanotubes/polydimethylsiloxane composites (MWCNT/PDMS) with different SC structures and different electrical conductivity are molded in acrylonitrile-butadiene-styrene copolymer (ABS) molds which are printed by a 3D printer. The results show that the electromagnetic interference shielding effectiveness (EMI SE) of the samples can be enhanced by constructing the SC micro-arrays with zig-zag micro-arrays, and improving with the increase of conductivity and frequency. In addition, the shielding mechanism of the SC-MWCNT/PDMS composites is investigated and discussed by an electromagnetic simulation.