Rev.Adv.Mater.Sci. (RAMS)
No 6, Vol. 18, 2008, pages 497-500

EFFECT OF MILLING MEDIUM ON THE STRUCTURE AND MAGNETIC PROPERTIES
OF MECHANICALLY ALLOYED BARIUM FERRITE

Waldemar Kaszuwara, Artur Witkowski, Marcin Leonowicz,
Piotr Pawlik and Józef Paszula

Abstract

Mechanical alloying of the mixture of Fe2O3 and BaCO3 powders in water leads to partial decomposition of barium carbonate and probably formation of barium hydrate Ba(OH)2. Application of steel vials for the milling in water results in their faster abrasive wear which is accompanied by enrichment of the powders in iron, in the form of Fe3O4 phase. Phase constitution of the materials studied after ferritization at 1000 úC/1h obtained by milling in water, consists of BaFe12O19 matrix with BaFe2O4 and Fe3O4 precipitates, whereas the sample obtained by milling in air contains only BaFe12O19 matrix with numerous Fe3O4 precipitates. The change in the microstructure does not explain however the differences observed in the magnetic properties, especially in the shape of the hysteresis loops. After milling in water the demagnetisation is dominated by nucleation of reverse domain whereas for the specimen milled in air conditions of pinning to the coercivity mechanism is evidenced.

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