Application of self-combustion method for synthesis of aluminum-substituted barium hexaferrite

Oxide materials have traditionally attracted the attention of researchers around the world. This is due to their wide range of applications: electrical engineering, electronics, special coatings, chemical technologies, etc. Doping of oxide materials with various elements such as Al, Bi, Zn, Co, Sn, Ti, B, Sb and others is widespread in order to fine-tune their physicochemical properties. In particular, doping of barium hexaferrite with aluminum is of particular interest, since this allows one to change such important parameters as saturation magnetization (σS), coercive force (HC), squareness coefficient of the hysteresis loop (K), as well as to influence the anisotropy field and microwave properties of the material. Since the preparation of BaAlxFe12-xO19 by the classical ceramic method requires thorough grinding of the starting materials, preliminary sintering, high temperature (above 1300 °C) and duration of the synthesis, it was decided to test an alternative method for obtaining aluminum-substituted barium hexaferrite. As such, we have chosen the self-combustion method. During the synthesis a solution of nitrates of the corresponding metals with citric acid was prepared. After neutralization and evaporation of the solution, the resulting mass was heated in a muffle furnace to carry out the spontaneous combustion process and remove residual carbon. The final sintering of samples with the composition BaAlxFe12-xO19 (for x = 0, 1, 2, and 3) was carried out in a muffle furnace with a precision temperature controller at 1100 °C for 4 hours. The obtained samples were studied by the powder diffractometry method, scanning electron microscopy, and X-ray spectral microanalysis. It has been established that the self-ignition method makes it possible to obtain homogeneous samples of barium hexaferrite substituted with aluminum at a lower temperature compared to the classical ceramic method. The parameters of the structure of the obtained samples were also determined. The tested method not only makes it possible to obtain aluminum-substituted barium hexaferrite at lower temperatures, but also makes it possible to dope ferrites with highly volatile elements.