Engineering polarization surface of hierarchical ZnO microspheres via spray-annealing strategy for wide-frequency electromagnetic wave absorption

•Hierarchical ZnO microspheres were successfully synthesized via spray-annealing strategy.•Pure dielectric loss ZnO materials were assembled by nanorods and nanoparticles with adjusting different aspect ratios, defects and polar faces.•Hierarchical ZnO-1 materials shown the widest efficient absorption region from 9.9 to 18.0 GHz at 2.4 mm.