The influence of aluminium and titanium substitution in barium hexaferrite BaFe(12-2x)TixAlxO19 on its structure and properties

The study of ferrites is currently one of the most important directions in scientific field, which is confirmed by a large number of publications on this topic. Ferrites are promising materials to be used in high-frequency electronics. The ferrite with the structure of magnetoplumbite is the most promising for the needs of microwave electronics, namely, barium hexaferrite BaFe12O19, as well as solid solutions based on it. The substitution of iron atoms in the structure of barium hexaferrite by other elements such as aluminum or titanium leads to significant changes in physical properties such as magnetic permeability, saturation magnetization, coercive force, Curie temperature, ferromagnetic resonance frequency, electrical conductivity. Thus, understanding how each of the iron-substituting elements affects the physical properties of a solid solution based on barium hexaferrite gives us the opportunity to smoothly adjust the characteristics of ferrite for a specific engineering task. The present paper studies the effect of the substitution of iron in the structure of barium hexaferrite by the aluminum and titanium atoms upon the change in parameters of the crystal lattice and physical properties. Monophase samples based on barium hexaferrite of the BaFe12O19, BaFe11AlO19, BaFe11TiO19, and BaFe11Al0.5Ti0.5O19 compositions were obtained by the solid-phase synthesis. The degree of substitution of iron by aluminum or titanium, as well as joint substitution by aluminum and titanium was the same for all samples. The resulting samples were studied by X-ray diffractometry, electron microscopy, and differential scanning calorimetry. According to the X-ray diffraction analysis data, the patterns of changes in parameters of the crystal lattice were revealed following the atom substitution. The Curie temperature for all the studied samples was measured by the method of differential scanning calorimetry. Conclusions are drawn about the influence of the substituting element on the Curie temperature value.