Influence of stoichiometry and heat treatment conditions on the magnetic properties and phase constitution of Ba-ferrite powders prepared by sol―gel

摘要

The magnetic properties and the microstructure of Ba-ferrite powders prepared by the sol-gel route were investigated. Amorphous gels were processed with a varying Fe/Ba ratio and then powder materials were obtained by heat treating at temperatures between 900 and 1000℃ for 1―4h. The results showed that increasing time and temperature was beneficial to the saturation magnetisation (M_s), whereas the coercivity (H_(ci)) was only slightly affected. The variation of the Fe/Ba ratio led to the formation of different proportions of BaFe_(12)O_(19) and BaFe_2O_4, which directly affected the magnetic properties. Transmission electron microscopy (TEM) micrographs showed mainly hexagonal-like grains with crystallite sizes ranging from ～50 to 150 nm.