Synthesis of barium hexaferrite by the self-combustion method

Until now, the ceramic method remains the most common for synthesis of complex oxides. In this case powders of oxides, carbonates or hydroxides of the required metals are sintered in air or in a controlled atmosphere after thorough mixing. However, it has several disadvantages. The most significant of them is the need to achieve high synthesis temperatures, which leads to an increase in the particle size. In addition, due to the latter circumstance, the resulting materials have a low specific surface area, which makes it impossible to use them as catalytic materials. The main advantages of this method are: low cost and availability of initial reagents, no need to use solvents, simplicity of the procedure, and a wide range of materials obtained. The results of obtaining barium hexaferrite BaFe12O19 by the self-combustion method are presented. During the synthesis, a solution of nitrate salts of the corresponding metals with citric acid was prepared. After neutralization and evaporation of the solution, the resulting sample was heated in a furnace to carry out the spontaneous combustion process and remove residual carbon. The final sintering was carried out in a tube furnace with a precise temperature controller. The samples obtained were investigated by the powder diffractometry, scanning electron microscopy, X-ray spectral microanalysis, and thermal analysis. It was found that the spontaneous combustion method made it possible to obtain homogeneous barium hexaferrite at a lower temperature (by 200 °C) in comparison with the classical ceramic method. For the synthesized BaFe12O19, the structural parameters are a = 5.891 Å, c = 23.215 Å, V = 697.6 Å3. The used method makes it possible to synthesize promising oxide materials with developed surface under milder conditions, as well as to alloy oxides with highly volatile elements.