One-step synthesis of barium hexaferrite nano-powders via microwave-assisted sol–gel auto-combustion

Single phase barium hexaferrite nano-powders have been innovatively one-step synthesized via a microwave-assisted sol–gel auto-combustion in a specially designed quartz vessel using citric acid and ethylene diamine tetraacetic acid as composite chelating agents and freeze-drying technique to remove sols’ moisture. The auto-combustion product powder is characterized by fluffy particle aggregates with the crystallites ranging from 50 to 100 nm in diameter and containing single magnetic domains for each with a low apparent coercive field of 260 Oe and a high saturation magnetization of 64.1 emu/g. The direct formation of barium hexaferrite is believed to result from the effective improvement in the spatial distribution homogeneity of metal ions and oxidant in the gels. Moreover, the quartz vessel with barium hexaferrite ceramic pad on sample's support and film-strips on its interior wall can effectively build up a favorable temperature environment to promote the direct formation of barium hexaferrite with microwave assistance during the gel's uniform auto-combustion.