Nano-architectured NiO shell vs 3D microflowers morphology toward enhancement of magneto-electric loss in mesoporous magneto-electric composite

The present study highlights two approaches for improving microwave absorption performance of SrFe12O19/ CoFe2O4/NiO (Sr/Co/NiO) composite. In the first approach, nickel oxide (NiO) nanopowder with polyhedral morphology was decorated on each magnetic mesoporous microsphere of Sr and Co prepared via solvothermal method (NiO@Sr/NiO@Co). In the second approach, NiO powder with 3D microflower morphology, with specific surface area of 74 m2/g, was synthesized via hydrothermal method and physically blended with mesoporous SrFe12O19 and CoFe2O4 magnetic microspheres (F-NiO/Sr/Co). The components weight proportion was adjusted to be the same for both composites and all features were evaluated by XRD, FESEM, BET, VSM and VNA analyses. For comparison purposes, reflection losses (RL) are also evaluated for usual (Sr/Co/NiO) composite prepared by blending the components, all of polyhedral morphologies (P-NiO/Sr/Co). RL results show that both F-NiO/Sr/ Co and NiO@Sr/NiO@Co have better microwave absorption performance than P-NiO/Sr/Co indicating the success of the two investigated approaches. However, the microwave performance of the core-shell structure composite NiO@Sr/NiO@Co is far better than that of F-NiO/Sr/Co, owing to the presence of multiple interfaces and junctions that give rise to interfacial polarization The minimum RL value for NiO@Sr/NiO@Co sample with 20% concentration reached -36 dB with 3.9 GHz effective bandwidth for just 2 mm thickness.

Automated summary

This study highlights two approaches to improve the microwave absorption performance of SrFe12O19/CoFe2O4/NiO composite, by using different morphologies of nickel oxide nanoparticles and 3D microflower NiO powder physically blended with magnetic microspheres. The core-shell structure composite NiO@Sr/NiO@Co showed better microwave absorption performance compared to the other composite, likely due to the presence of multiple interfaces and junctions leading to interfacial polarization. The successful enhancement of microwave absorption efficiency was demonstrated through the minimum reflection loss value and effective bandwidth of the NiO@Sr/NiO@Co sample.