Different crystal structure evolvement and the electromagnetic properties of nano-Manganese Dioxide

MnO2 with different morphology and crystal structure were prepared via a low-temperature hydrothermal method in stainless-steel autoclave at 120℃ and different dwell time, which (NH4)2S2O8 is oxidizing agent and MnSO4 is Mn source. The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM), and the electromagnetic properties and microwave loss mechanism of as-obtained MnO2 were firstly reported. The results show that the dwell times play a crucial role in the phase purity, the crystal structure, the morphology and the electromagnetic properties of the products. The as-prepared MnO2 transformed gradually from γ-MnO2 to α-MnO2 and β-MnO2 and became finally a pure tetragonal phase of β-MnO2, and the morphology changed also from microspheres with flocculus on the surface into dispersive nanorods with the increase of the dwell times from 1h to 48h. The real and imaginary parts of the complex permittivity of as-prepared MnO2 increased orderly with rising dwell times, and the complex magnetic permeability were on the contrary. Lastly, the microwave loss mechanism of as-obtained MnO2 was analysed.