Impact of the heat treatment conditions on crystal structure, morphology and magnetic properties evolution in BaM nanohexaferrites.

Present paper reports about the strong correlation of the heat treatment conditions (annealing), crystal structure parameters, microstructure and magnetic properties evolution in nanosized BaFe 12 O 19 M-type hexaferrites or BaM nanohexaferrites. Samples of the BaM nanohexaferrites were obtained using sol-gel method with further annealing in the range 600–1100 °C. All investigated samples were single phase and described by the P 6 3 / mmc space group. Unusual and non-linear behavior of the lattice parameters with annealing temperature increasing from 600 to 1100 °C was explained by the competition of the increase in the average crystallite size (decrease in the surface tension effect) and increase in the level of their chemical homogeneity (anionic stoichiometry). Increase of the heat treatment temperature leads to increase of the microstructure parameters (average crystal size and specific surface area) and non-linear changes in magnetic properties. Correlation of the annealing temperature and magnetic properties was discussed in terms of the structural features. • BaM nanohexaferrites were synthesized using sol-gel method with further annealing. • Strong correlation between average crystal size and annealing temperature was established. • Non-linear behavior of the structure and magnetic properties after annealing was observed. • All changes in BaM were discussed in terms of the morphology evolution. [ABSTRACT FROM AUTHOR]