Sol-gel synthesis of nanodispersed solid solutions based on barium hexaferrite SrxBa(1-х)Fe12O19

The present paper provides data on the sol-gel synthesis of M-ferrite with the SrxBa(1-x)Fe12O19 (х = 0; 0.3; 0.5; 0.7; 1) composition. The synthesis technique is based on the preparation of a polymeric citrate complex from citric acid and nitrates of barium, strontium, and iron, its calcination at 500 °C followed by mechanochemical activation, and calcination at 700 °C. The target product is a dark brown powder, which has been studied by the XRD and SEM methods, energy-dispersive X-ray spectroscopy and differential scanning calorimetry (DSC). The single-phase state of the obtained samples is confirmed by powder X-ray diffraction. The X-ray patterns of the synthesized hexaferrites match the X-ray patterns of reference compounds from the ICDD database for all diffraction maxima. The unit cell parameters of the samples have been calculated from the X-ray diffraction patterns. They linearly depend on the degree of barium substitution in hexaferrite, that is, the successful replacement of barium ions in the crystal lattice by strontium ions, due to the Vegard rule for solid solutions. Morphological parameters have been studied using SEM, the analysis of the obtained images indicates the formation of nanodispersed hexaferrites, for which the average particle size is 50 nm. The average particle size, calculated by the Scherrer's formula, equals 25 nm. The usual hexagonal form of hexaferrite particles has not been observed in the SEM images due to the small particle size. Energy-dispersive X-ray spectroscopy of the obtained images indicates a high degree of homogenization for the chosen synthesis technique. Using the DSC method we obtained values of Curie temperature which show it’s increases linearly with an increasing of Sr weight percent.