Single-phase Mn_(1-x)Zn_xFe_2O_4(x = 0.2, 0.5,0.8) hollow ceramic microspheres: One-step preparation and electromagnetic properties

摘要

Single-phase Mn_(1-x)Zn_xFe_2O_4 (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 20-60μm; 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, Mn_(0.8)Zn_(0.2)Fe_2O_4 HCMs and Mn_(0.2)Zn_(0.8)Fe_2O_4 HCMs have higher real part of permittivity (ε') value than Mn_(0.5)Zn_(0.5)Fe_2O_4 HCMs. Owing to higher conductivity, the value of imaginary part of permittivity (ε") of Mn_(0.5)Zn_(0.5)Fe_2O_4 HCMs was the highest in 0.1-0.8 GHz range, however, with the frequency increases, the ε" of Mn_(0.8)Zn_(0.2)Fe_2O_4 HCMs and Mn_(0.2)Zn_(0.8)Fe_2O_4 HCMs increased significantly resulting from orientation polarization and interfacial polarization, which was greater than Mn_(0.5)Zn_(0.5)Fe_2O_4 HCMs. Due to the higher Ms, the value of imaginary part of permeability (μ") of Mn_(0.2)Zn_(0.8)Fe_2O_4 HCMs and Mn_(0.8)Zn_(0.2)Fe_2O_4 HCMs was greater than Mn_(0.5)Zn_(0.5)Fe_2O_4 HCMs. Moreover, the μ"-f curve reveals a broad resonance peak of Mn_(0.8)Zn_(0.2)Fe_2O_4 HCMs ranging from 0.1 to 8 GHz, which maybe relate to its thick nano-lamellar crystal.