Preparation of barium hexaferrite by a hydrothermal method: structure and magnetic properties

Barium hexaferrite, BaFe¹²O₁₉, was obtained in hydrothermal conditions from a water suspension of -FeOOH and Ba(OH)₂ · 8H₂O at a temperature about 315° C. X-ray and Mössbauer spectroscopy as well as electron microscopy investigations demonstrated the appearance of -Fe₂O₃ as an intermediate phase in the hydrothermal process. The magnetic characteristics of the obtained isotropic magnets are the following: coercive fieldH _c 159 kA m^–1, residual inductionB _r 0.26 T, maximum energy product (BH) _max12 kJ m^–3. The hydrothermal procedure for the preparation of barium hexaferrite in comparison with the conventional one is discussed.