Magnetic Nanocrystalline Mg0.5Zn0.5Fe2O4: Preparation, Morphology Evolution, and Kinetics of Thermal Decomposition of Precursor

Abstract

Mg0.5Zn0.5Fe2(C2O4)3⋅H2O was synthesized by solid-state reaction at low heating temperatures using MgSO4⋅7H2O, ZnSO4⋅7H2O, FeSO4⋅7H2O, and Na2C2O4 as raw materials. The spinel Mg0.5Zn0.5Fe2O4 was obtained via calcining Mg0.5Zn0.5Fe2(C2O4)3⋅H2O above 400 °C for 1 h in air. The Mg0.5Zn0.5Fe2(C2O4)3⋅H2O and its calcined products were characterized by thermogravimetry and differential scanning calorimetry (TG/DSC), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The results showed that Mg0.5Zn0.5Fe2O4 obtained at 400 °C had a specific saturation magnetization of 27.3 emu g−1. The thermal process of Mg0.5Zn0.5Fe2(C2O4)3⋅H2O experienced three steps, which are: first, the dehydration of water of crystallization and decomposition of Mg0.5Zn0.5C2O4 into MgO and ZnO, then the reaction of Fe2(C2O4)3 with MgO and ZnO into amorphous Mg0.5Zn0.5Fe2O4, and at last the crystallization of Mg0.5Zn0.5Fe2O4. Based on the KAS equation and the OFW equation, the values of the activation energies associated with the thermal process of Mg0.5Zn0.5Fe2(C2O4)3⋅H2O were determined to be 69±11 and 71±9 kJ mol−1 for the first and second thermal process steps, respectively.