Synthesis of nonstoichiometric M-type barium ferrite nanobelt by spark plasma sintering method

This study investigated the feasibility of ul-trafast crystallization of M-type barium ferrite when the coprecipitation precursors in stoichiometric proportions as BaFe12O19, Fe(OH)3 and BaCO3 nanoparticles, had been heated by spark plasma sintering (SPS) process. The results show that SPS method may realize the ultrafast crystalliza-tion of M-type barium ferrite, absolutely prevent the crystal-lization of intermediate phase α-Fe2O3, and significantly decrease the crystallization temperature of M-type barium ferrite. The sintered samples obtained at 800℃ by sintering the precursors for 10 minutes are a kind of multiphase fer-rites composed of major phase M-type barium ferrite and trace amount of BaFe0.24Fe0.76O2.88. It is discovered that M-type barium ferrites in the holes of the sintered samples are in nanobelt microstructure about 100-300 nm in width and several micrometers in length. These M-type barium ferrite nanobelts are non-stoichiometric and may be ex-pressed as BaFe12+xO19+1.5x (?4.77≤x≤6.50). Their com-posistions suggest completely random Fe-rich or Ba-rich domains.

This study investigated the feasibility of ultrafast crystallization ofM-type barium fertile when the coprecipitation precursors in store Mometric proportions asBaFe_(12)O_(19), Fe(OH)_3 and BaCO_3 nanoparticles, had been heated by spark plasma sintering (SPS)process. The results show that SPS method may realize the ultrafast crystallization of M-type bariumferrite, absolutely prevent the crystallization of intermediate phase a-Fe_2O_3, and significantlydecrease the crystallization temperature of M-type barium ferrite. The sintered samples obtained at800 deg C by sintering the precursors for 10 minutes are a kind of multiphase ferrites composed ofmajor phase M-type barium ferrite and trace amount of BaFe_(0.24)Fe_(0.75)O_(0.58). It is discoveredthat M-type barium ferrites in the holes of the sintered samples are in nanobelt microstrnctareabout 200-300 nm in width and several micrometers in length. These M-type barium ferrite nanobeltsare non-stoichiometric and may be expressed as BaFe_(12+x)O_(19-1.5x) (-4.77 < =x <= 6.50). Theircomposistions suggest completely random Fe-rich or Ba-rich domains.