The synthesis of barium hexaferrite from iron oxide and barium carbonate: II. The role of iron oxide texture

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Abstract
The texture of several samples of laboratory‐prepared and commercial iron oxide and their reactivity with barium carbonate (BaCO3.6Fe2O3) has been examined. The first stage of the reaction involves decarbonation with the formation of monoferrite and dynamic thermogravimetry was used to assess mix reactivity. While some of the variation in the behaviour of iron oxide powders could be appreciated from an examination of their texture by scanning electron microscopy and porosity determination, prediction of their reactivity was not possible. In fact the reactivity of the mix can best be considered to give an indication of the efficiency of mixing of the finer iron oxide particles with the barium carbonate. In the subsequent formation of barium hexaferrite the coarse end of the iron oxide particle size range is of primary importance since it controls the rate of completion of the reaction. The larger aggregates in an iron oxide sample can readily be detected by scanning electron microscopy but conclusions regarding reactivity may be erroneous if this coarse material is dispersed during mixing. It was shown by scanning electron microscopy that the least reactive iron oxide sample examined contained aggregates which survived the mixing process employed.