Production of strontium hexaferrite based ferritic magnet powder using hematite from domestic scale

Magnets are the most important components of many systems such as electric motors of today's electric vehicles, magnetic resonance imaging (MR) devices, speakers and headphones. Due to the lack of magnet production in our country and the widespread use of magnets in the above-mentioned sectors, the need for magnets has increased significantly both in our country and in the global market. Therefore, there was a need to work on the production of magnet powder using our domestic raw materials. Within the scope of this study, domestic iron oxide material, called scale, was purchased from companies operating in the iron and steel industry in Turkey and synthesized with strontium carbonate to produce strontium hexaferrite-based magnet powder. The scale samples were tried to be converted into hematite phase by subjecting them to heat treatment and mechanical grinding processes. The crystal phases and elemental content of 10 different scale samples were analyzed semi-quantitatively by the XRD device and the samples with the highest hematite content were determined. These samples and readymade commercial iron oxide samples from China were synthesized with strontium carbonate material in 12 different ways in the range of 1.5 – 1.6 stoichiometric ratios. A high-energy ball mill was used in the synthesis processes, and the mechanically alloyed synths were heat treated in a sintering kiln furnace. Due to the agglomeration of the final syntheses during the heat treatment, wet grinding process was carried out and strontium hexaferrite slurry was tried to be obtained at the micron level. These synthesis slurries were dried in a fume hood by means of a heater and made suitable for crystal structure analysis. The crystal structures of the obtained dry syntheses were observed by the XRD device and the strontium hexaferrite synthesis with the highest ratio was determined as K21. The magnetic performance of the K21 sample was compared with the magnetic performance of commercial magnet powder of grade Y30, ready-made from China, by means of the VSM - Vibrating Sample Magnetometer device. Based on the results of the analysis, it was observed that the strontium hexaferrite powder obtained with domestic iron oxide reached 15 times lower Hc (coercivity) value than commercial magnet powder. Key words: Strontium hexaferrite, permanent magnets, mechanochemical synthesis