Abstract: Single phase barium hexaferrite nanocrystals were innovatively onestep synthesized via a microwave-assisted sol-gel auto-combustion method using citric acid and ethylene diamine tetraacetic acid as composite chelating agents, and freeze-drying technique was used to remove sols’ moisture that effectively improve the spatial distribution homogeneity of metal ions and oxidant in the gels. The obtained barium hexaferrite nanocrystals is characterized by fluffy particle aggregates with the diameter ranging from 50nm to 100nm. The nanocrystals contain single magnetic domains with a low coercive field of 20.7kA/m and a high saturation magnetization of 338.5kA/m. The analysis shows that keeping rich oxidant in the autocombustion process can prohibit the reduction of iron ions by the organic fragment from the decomposition of fuels and promote the phase formation of barium hexaferrite.

Key words: barium hexaferrite, microwaveassistance, sol-gel auto-combustion, onestep synthesis