Formation and microwave absorption of barium and strontium ferrite prepared by sol-gel technique

Abstract

Ba and Sr ferrites are prepared by sol-gel technique with different Fe/Ba(Sr) ratios in the starting materials. Magnetization, coercive, and anisotropy field strength are determined depending on the heat treatment of the gel and the iron/barium(strontium) ratio in the starting material. A two-step heat treatment is used to prepare single-domain powders with high magnetization. These powders prepared by sol-gel technique show single-domain behavior with specific magnetization σS=649 A cm2/g and coercive field strength HcM=402 kA/m in the case of Ba ferrite and σS=695 A cm2/g and HcM=416 kA/m for Sr the ferrite. Al-substituted ferrites with high anisotropy field strengths are prepared additionally. Ferromagnetic resonance absorption is used to determine the anisotropy field strength and to investigate the formation process of the hexaferrite phase during the heat treatment. The beginning of hexaferrite formation occurs at annealing temperatures below 700 °C.

High-Resolution Transmission Electron Microscopy Studies of Sol–Gel-Derived Cobalt-Substituted Barium Ferrite

“…Over the past few decades, the sol-gel method has been used extensively to produce fine particles of a variety of oxides (1)(2)(3)(4). With the increasing demands for an erasable high bit density data storage system, fine particle of cationsubstituted barium ferrite are widely anticipated to be a suitable candidate for future high-density magneto-optical recording (5).…”

Synthesis and characterization of magnetic nanocomposites of fullerene‐containing polyurethane films for microwave applications

“…Compared with the ferrites with spinel and garnet structure, hexagonal barium ferrites can be used as good microwave absorber in the frequency range of 1 to more than 20 GHz because of their high saturation magnetization, unusually large coercivity, excellent chemical stability, corrosion resistance, and adjustable anisotropy through ion doping. [7][8][9] BaFe 12 O 19 (BaFe), a well known permanent magnet having a magnetoplumbite-type structure (hexagonal) with fairly large crystal anisotropy along C-axis, has attracted an extensive attention for the last few decades. 10,11 However, ferromagnetic materials have a serious defect plaguing microwave absorbers applications, namely eddy current losses.…”

Synthesis, characterization and magnetic properties on nanocrystalline BaFe12O19 ferrite

“…Also along with further research and increasing demands for microwave communication, microwave dark room, the anti-electromagnetic wave radiation, the barium ferrite has been caused great attention [1][2][3][4]. In order to get high-powered barium ferrite, people are trying their best to obtain pure crystalline mono-domain particles of BaFe 12 O 19 , different synthesis techniques have been developed, such as sol-gel technique [5], microemulsion [6], hydrothermal reaction [7], glass crystallization [8], salt-melt technique [9], etc. Particularly, sol-gel technique is a new method which can be used to prepare for high-powered nanocrystalline BaFe 12 O 19 .…”