NiZnFe2O4 core-shell nanoflowers as effective EMI shielding material dedicated to the absorption of electromagnetic waves in the UHF band and wide temperature range

Thin, non-conductive electromagnetic interference shielding materials with high absorption efficiency and temperature stability in the UHF band are still in demand. Therefore, we propose a single-step synthesis method of NiZnFe ₂O ₄ core-shell nanoflowers (NFs) with high shielding efficiency (SE) and reflection losses (RL). NiZnFe ₂O ₄ NFs comprise an oxidized shell and spinel core, providing high magnetic and dielectric losses. The attenuation constant was high and increased slightly with temperature from 329 to 340 Np/m (at 2.1 GHz). Also, temperature-induced changes in SE and RL were negligible. The analysis confirmed the applicability potential in the UHF band. For example, at 1.2 GHz, an SE equal to -13.53 dB can be achieved for 3 mm and -38 dB at 2 GHz for 4 mm absorber thickness. Moreover, increasing the thickness to 5.73 mm shifts the absorption range even to 0.88 GHz, while 2 mm absorbers can be used above 2 GHz.