Enhancing magnetism of ferrite via regulation of Ca out of sit A from spinel-type structure by adjusting the CaO/SiO2 mass ratio: Clean and value-added utilization of minerals

Ferrites with a typical AB 2 O 4 structure are excellent soft magnetic material precursors . One progress for preparation of manganese ferrite is to use the minerals as raw materials. However, the inclusive impurities, such as Ca and Si, may dope in the AB 2 O 4 structure and have an adverse effect on the magnetism of ferrites. In this work, the effects of CaO and SiO 2 on the crystalline structure transformation, interfacial elements distribution, and magnetism change of the MnO 2 -Fe 2 O 3 -CaO-SiO 2 system for preparation of high-performance ferrite materials were systematically investigated. It's found that Ca ions can readily be doped in the sit A of spinel-type structure to form Ca a Mn b Fe 2 O 4 , and the magnetism of manganese ferrite was observably declined due to the Ca doping. A diffusion couple of synthetic Ca a Mn b Fe 2 O 4 and SiO 2 was designed to determine the Ca migration. Results demonstrated that regulation of Ca out of sit A from the spinel-type structure can be successfully realized via adjusting the CaO/(CaO ​+ ​SiO 2 ) mass ratio below 0.55, and the magnetism of ferrite after Ca migration was obviously enhanced. The migrated CaO combined with SiO 2 to form calcium silicate which was distributed at the boundaries of ferrite particles. Eventually, the verification test of low-grade manganese ores with CaO and SiO 2 impurities was conducted to validate the Ca migration effect.