Single-phase Mn1−xZnxFe2O4(x = 0.2, 0.5, 0.8) hollow ceramic microspheres: One-step preparation and electromagnetic properties

Single-phase Mn1−xZnxFe2O4 (x = 0.2, 0.5, 0.8) hollow ceramic microspheres (MnZn-HCMs) was one-step prepared using self-reactive quenching method. Material parameters of three MnZn-HCMs were studied by SEM and XRD, and electromagnetic properties were investigated by vibrating sample magnetometer and vector network analyzer. The results showed that the phase composition of three MnZn-HCMs presents single-phase, with particle size distribution of 20–60 μm; when x was equal to 0.2 or 0.8, the surface of HCMs showed a large number of nano-lamellar crystal with crossing, connecting or laminating each other, and for 0.5, a large quantity of nano-isometric crystal was formed. Thanks to special surface structure and micron-particle size, three MnZn-HCMs exhibited superparamagnetic. With the content of Zn increases, the saturated magnetization (Ms) decreases first and then increases, meanwhile, the coercivity (Hc) decreases gradually. In the 0.1–18 GHz range, due to nano-lamellar structure could enhance the interfacial polarization and space charge polarization, Mn0.8Zn0.2Fe2O4 HCMs and Mn0.2Zn0.8Fe2O4 HCMs have higher real part of permittivity (ε′) value than Mn0.5Zn0.5Fe2O4 HCMs. Owing to higher conductivity, the value of imaginary part of permittivity (ε″) of Mn0.5Zn0.5Fe2O4 HCMs was the highest in 0.1–0.8 GHz range, however, with the frequency increases, the ε″ of Mn0.8Zn0.2Fe2O4 HCMs and Mn0.2Zn0.8Fe2O4 HCMs increased significantly resulting from orientation polarization and interfacial polarization, which was greater than Mn0.5Zn0.5Fe2O4 HCMs. Due to the higher Ms, the value of imaginary part of permeability (μ″) of Mn0.2Zn0.8Fe2O4 HCMs and Mn0.8Zn0.2Fe2O4 HCMs was greater than Mn0.5Zn0.5Fe2O4 HCMs. Moreover, the μ″-f curve reveals a broad resonance peak of Mn0.8Zn0.2Fe2O4 HCMs ranging from 0.1 to 8 GHz, which maybe relate to its thick nano-lamellar crystal.