Clean and economical preparation of Ca-La-Co substituted permanent ferrite magnet with ultrapure magnetite concentrate

Abstract

For the first time, ultrapure magnetite concentrate (UMC) was studied to prepare Ca-La-Co substituted magneto plumbite type (M-type) permanent ferrite magnet (PFM). UMC with a purity of 99.6 % was purified from magnetite concentrate. PFM prepared with UMC had fully reached the standard of La-Co substituted 9BF product of Pacific Metals (Br>420 mT, Hcj>374 kA/m) under the optimized chemical formula of Sr0.3Ca0.3La0.4Fe11.5Co0.3O18.7 and suitable process conditions. The PFM prepared with the UMC had higher Hcb and Hcj but lower Br and BHmax as Compared to the PFM prepared with the conventional high-quality iron oxide red. Impurities of SiO2 and Al2O3 in UMC thermodynamically formed Sr2Al2SiO7 in magnetic powder, which effectively inhibited abnormal grain growth but decreased the purity of main phase. UMC owns the merits of low raw material cost, large potential production capacity and almost pollution-free. The feasibility of UMC used for the high-performance PFM preparation has been confirmed and it has a promising prospect from the views of economic gains and environmental benefits.