Sintering behaviors of Mn–Zn–Fe oxide systems: Ternary formulas, phase compositions and electromagnetic properties

Manganese zinc (MnZn) ferrite is one of the most used ferrite materials, while the investigations on sintering behaviors and magnetic properties of MnZn ferrite with ultrahigh metal oxide components are important supplements to the preparation knowledge of MnZn ferrite. In the formula triangle of the Fe2O3–ZnO–MnO2 system, four representative formulas including 50%Fe–25%Zn–25%Mn, 80%Fe–10%Zn–10%Mn, 10%Fe–80%Zn–10%Mn, and 10%Fe–10%Zn–80%Mn were selective in this work to stand for medium-Fe, high-Fe, high-Zn, and high-Mn systems. The thermogravimetric aspects, phase compositions, microstructure features, magnetic properties, electromagnetic parameters, and electromagnetic wave absorbing properties of four samples were compared via the TG-DSC, XRD, XPS, SEM-EDS, VSM, and VNA analyses. It's suggested that the phase compositions and microstructures were dramatically affected by the iron content. After sintering, the high-Fe and medium-Fe systems present single ZnxMnyFe2O4 (0 < x, y < 1) phase and condense structure, while some free superfluous oxides are concomitant in the high-Mn and high-Zn systems. The pore structure and number are positively correlated with the MnO2 content in the Mn–Zn–Fe oxide system owing to the decomposition deoxygenation reaction. The magnetism study indicates that all four samples present good soft magnetic properties and less coercive force, while the high-Fe system displays the highest magnetic saturation intensity of 102 emu/g and the lowest magnetic coercivity. Due to the uniform composition, dense structure, and sufficient iron ingredient, the as-prepared MnZn ferrite with the formula of 80%Fe–10%Zn–10%Mn (high-Fe system) sintered at 1300 °C for 6 h demonstrates strong electromagnetism performance with the minimum RL peak of −42.03 dB at a veneer thickness of 8 mm. It's suggested that sintered MnZn ferrite with high-iron content demonstrates superior electromagnetic wave absorption properties. This work provided a batching formula foundation for the preparation of high-performance MnZn ferrites with high metal oxide constituents from pure oxide reagents or mineral materials.