Effects of temperature and time on microstructure and microwave electromagnetic properties of Ni doped manganese dioxides

With KMnO4 as the oxidant and MnSO4 as the manganese source, the chemically synthesised alpha-MnO2 powder was carried out to investigate the effects of temperature and time on the microstructure and microwave electromagnetic properties of Ni doped alpha-MnO2. The obtained samples were characterised by XRD, SEM, and vector network analysis. The results showed that the products would transmit from alpha-MnO2 and gamma-MnO2 to Mn3O4, when the temperature increased to 100 degrees C with 3 h reaction time in the certain conditions, the morphologies did not change remarkably and the dielectric property had a big change: the real and imaginary part of the complex permittivity and dielectric loss tangent all decreased, the dielectric loss properties changes bad with the increase of reaction temperature and the extension of time. The phenomenon may be connected with the improvement of crystallinity and the reduction of crystal defects with the increase of reaction temperature and the extension of time. The relative low synthesis temperature and short reaction time are useful to obtain the Ni doped MnO2 with strong microwave absorption performance.