Electromagnetic Properties and Growth Mechanism of Manganese Dioxide Powder with Self-grown Core-Shell Structure

MnO2 powder with self-grown core-shell structure was prepared by hydrothermal synthesis using(NH4)(2)S2O8 as the oxidizing agent and MnSO4 center dot H2O as the Mn source. The composition, crystal shape, morphology, magnetic characteristic and thermal stability of the samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM), vibrating sample magnetometry(VSM) and thermogravimetric analysis(TG, DTA), respectively. In addition, the electromagnetic properties and microwave loss mechanism of MnO2 specimens are discussed based on the tested electromagnetic parameters, such as the dielectric constant and permeability. The results show that MnO2 powders have a self-grown core-shell structure with diameters of 3 similar to 5 mu m, the real and the imaginary part of the complex relative permittivity are 8.40 similar to 5.35 and 2.66 similar to 2.07, respectively, whereas the real and imaginary part of the complex permeability are as small as 1.04 similar to 1.14 and 0.03 similar to 0.21, respectively. Finally, the microwave loss mechanism and the thermally stable performance of MnO2 with core-shell structure are suggested.