A crystallization conditions study of the Ti‐doped barium hexaferrite powders synthesized with the glass crystallization technique for microwave applications

Abstract

For microwave applications Titanium doped M-type hexagonal ferrites have been synthesized by means of glass crystallization technique varying the crystallization parameters and the melt doping concentrations. The chosen melt dopings were x = 5.4 and 7.2 mole-% TiO 2 with the following basic composition (mole-%): 40 BaO + 33 B 2 O 3 + (27-x) Fe 2 O 3 + x TiO 2 . We have studied the dependencies between the magnetic properties, the valence of the iron ions in the glasses and the powders, the formation of new dielectric phases and the microwave absorption. After the Ti 4+ ions substitutions, the magnetocrystalline anisotropy changed, this effect was observed in the static magnetic properties ( J H C and M S ) measured using a vibration sample magnetometer. Furthermore the Ti 4+ ions preferably occupy mainly the 2a as well as slightly the 2b sites in the lattice of the barium hexaferrite, which are studied using Mössbauer spectroscopy. Besides, the X-ray diffraction studies proved that the formation of the ferrimagnetic (BaFe 12-x Ti x O 12 ) and dielectric (BaTi 6 O 13 ) phases are dependent on the crystallization parameters. The controlled influencing of lattice sites occupation and of the Fe 2+ content in the ferrimagnetic phase as well as the controlled formation of the dielectric phase rate during the annealing are possibilities to optimize the microwave absorption of Ti-doped barium hexaferrite powders synthesized by glass crystallization technique.Keywords: barium hexaferrite / microwave absorber / Mössbauer spectroscopy / titanium substitution / X-ray diffraction / Im vorliegenden Beitrag werden für Mikrowellenanwendungen Titan-dotierte hexagonale M-Typ Ferrite in einer schnellgekühlten Glasschmelze der Grundzusammensetzung (mol-%): 40 + 33 B 2 O 3 BaO + (27-x) Fe 2 O 3 + x TiO 2 mit der Glaskristallisationstechnik bei Variation der Schmelzdotierung und der Kristallisationsparameter hergestellt. Die gewählten Schmelzdotierungen sind x = 5,4 und 7,2 Mol-% TiO 2 . Dabei wird insbesondere der Einfluss der Schmelzdotierung und der Temperbedingungen auf die magnetischen Eigenschaften, die Wertigkeit der Eisenionen im Glas und in den Pulvern, die Phasenbildung im Glas und die Mikrowellenabsorption der Pulver untersucht.