Synthesis, characterization and microwave properties of Ni–Co–P hollow spheres

Ni–Co–P hollow spheres (HSs) with different component ratios were fabricated by autocatalytic reduction method. With an increase of cobalt content, coercivity of hollow spheres increased because of Co hcp structure with high magnetocrystal anisotropy. The microwave properties of Ni–Co–P HSs were investigated in the range of 2–18 GHz. Both permittivity and permeability of spheres–wax composites increased with the increase of cobalt content. For the Ni–Co–P hollow spheres, the minimum reflection loss (RL) (−41.7 dB) was found at 6.3 GHz with a thickness of 2.5 mm. Additionally, with the increase of cobalt content, the minimal reflection loss increases obviously, which means that introducing Co into Ni improves the microwave absorption capability.