Jadambaa Temuujin

Benefits of mild wet milling of the intermediates for the synthesis of phase-pure Z-type hexaferrite

A comparative study on the wet and dry milling of the intermediates for the Z-type hexagonal ferrite (Ba 3 Co 2 Fe 24 O 41 , Z phase) was performed. Phase-pure Z phase was synthesized by wet milling the intermediates comprising M and Y-type hexaferrites. The intermediates were obtained by calcining the stoichiometric powder mixture at 1080 °C. Subsequent wet milling by a planetary mill for 1 h increased the crystallization rate of Z phase upon subsequent heating at 1230 °C. In contrast, dry milling the intermediates resulted in the severe surface amorphization and led to heterogeneous crystalline states. The observed favorable effect of wet milling the intermediates was explained by the particle size reduction for the decrease of diffusion distance while preserving the basic layer units common to the related hexaferrites.

Crystallization of M-type hexagonal ferrites from mechanically activated mixtures of barium carbonate and goethite

M-type hexagonal ferrite precursor was prepared by a soft mechanochemical treatment of BaCO3 and α-FeOOH mixtures. The effect of milling on its structure and thermal behaviour was examined by XRD, SEM and FTIR. Well crystallizedM-type hexagonal ferrite was formed from just 1 h milled precursors at 800°C. The beneficial effect of milling was explained in terms of increased homogeneity with simultaneous hetero bridging bond formation between powder constituents.