PROTOCOL FOR THE SYNTHESIS OF BA-HEXAFERRITES WITH PREFIXED COERCIVITIES

The ferrite industry is one of the largest consumers of iron oxides, u sually in the form of hematite from the roasting of steel pickling liq uors or from mineral sources. In previous papers we have tested an oxi dation process for obtaining magnetite and goethite from steel picklin g liquors and two mathematical models have been proposed for synthesiz ing these two iron oxides. In this paper, the characteristics of magne tite and goethite are related with the coercivity of hexaferrites synt hesized when the former are used as raw materials. Constant conditions were used for the ceramic method. Using goethite, Ba-hexaferrite is o btained only when the goethite is precipitated at the lowest oxidizer flow. When magnetite is used, a protocol with a statistically validate d correlation is proposed for synthesizing hexaferrites with coercive fields between 230 and 450 kA/m. This correlation is valid for an oxid ation process carried out at stirring speed of 1000 rev/min and with a n air flow between 7.5 and 10 l/min. A second empirical correlation is proposed for obtaining final coercivities between 450 and 525 kA/m, f or which it is necessary to increase the calcination time.