HREM study of M, Y and W hexagonal type ferrites

Abstract

Hexagonal ferrites have similar structural symmetries and are built by the same structural units. HREM has proved to be an excellent tool to identify individual stacking bloks, in M, Y and W hexaferrites.M, Y and W hexagonal type ferrites are well-known magnetic materials for applications. Some previous electron microscopy studies on these ferrites, reveal a variety of new phases coming from the microsyntactic intergrowth of M, Y and W structures. We report in this paper some microstructural features of these ferrites.BaFe12O19 (M) hexagonal ferrite was synthetized by using the standard ceramic technique. Crystals of Y type ferrite (nominal composition: BaLi0.5Fe0.5ZnFe16027) were prepared from stoichiometric amounts of BaCO3, ZnO and LiCO3. The synthesis of W-type ferrite (formula: Ba2Zn2Fe16027) is described elsewhere.Samples for observation were prepared by grinding powders of the above ferrites under acetone. HREM study was performed at the "Centro de Microscopía Electrónica, Univ. Complutense" using both 400 Kv and 200 Kv electron microscopes (JEM-400EX and JEM-200FX)