Utilizing ultrapure magnetite concentrate for environmentally friendly and low-cost synthesis of high-performance strontium ferrite.

The presence of Al and Si impurities from ultrapure magnetite concentrate (UMC) entering the lattice during the preparation of M-type strontium ferrite (SrM) has been a significant issue limiting the enhancement of magnetic properties in UMC- prepared SrM. In this article, the impact of CaCO 3 on the phase formation mechanism of synthesizing SrM using UMC is investigated. It is found that the formation of intermediate SrFeO 3−x phase and SrFe 12 O 19 phase shifts to the lower temperatures upon CaCO 3 addition. Lower calcination temperatures can inhibit excessive grain growth, thereby improving coercivity. At a calcination temperature of 1050 °C with the addition of 0.6 wt% CaCO 3 , the highest coercivity of 4672.29 Oe was achieved. Lattice parameters, magnetic properties, and micro-area composition analysis demonstrate that the addition of CaCO 3 reacts with Al impurities, preventing the incorporation of Al ions into the SrM lattice and promoting an increase in saturation magnetization. The highest saturation magnetization of 71.45 emu/g was obtained at the calcination temperature of 1200 °C. It has reached the level of magnetic properties of SrM prepared from Fe 2 O 3. CaCO 3 , being low-cost and environmentally friendly, can serves as an effective additive for improving the magnetic properties of UMC-prepared SrM without compromising its cost-effective and eco-friendly advantages. • SrFe 12 O 19 was synthesized from ultrapure magnetite concentrate as raw materials. • Adding CaCO 3 reduces the formation temperature of intermediate and final phases. • Adding CaCO 3 weakens the adverse effect of Al impurity of raw materials. • Adding CaCO 3 improves the magnetic properties of synthesized SrFe 12 O 19. • SrFe 12 O 19 is produced cheaply and environmentally. [ABSTRACT FROM AUTHOR]