Self-propagating high-temperature synthesis of barium-chromium ferrites BaFe12-xCrxO19 (0 <= x <= 6.0)

Pure and chromium substituted barium ferrites BaFe12-xCrxO19 (0 less than o r equal to x less than or equal to 6.0) have been synthesised in air by sel f-propagating high-temperature synthesis (SHS): a combustion process involv ing a reaction of barium peroxide, iron oxide, chromium oxide and iron meta l powder Two series of SMS samples were produced: series 1-zero field SHS, and series 2-SHS in a magnetic field of 1.1 T,both followed by sintering at 1200 degrees C for 2 h. X-ray data showed that hexagonal ferrites were pro duced, and systematic changes in lattice parameters were seen as a function of the Cr content. Scanning electron microscopy indicated crystallites of order 1 mu m. Energy dispersive x-ray analysis (EDAX) showed that the sampl es were homogeneous with the; expected Ba:Fe:Cr ratios. Mossbauer, x-ray an d magnetic hysteresis data showed a progressive change in the sublattice oc cupancy and magnetization with Cr content. Some differences in magnetic: pa rameters were observed between series 1 and 2, implying that the use of a m agnetic field during SHS can influence product microstructure. In particula r the coercive forces in the Ct doped ferrites showed maxima at x = 1.5 and x = 1.0 for series 1 and 2 respectively, with the series 2 coercivities be ing consistently 40-50% smaller than their series 1 counterparts. This indi cates that applied held SNS provides an alternative route to reducing coerc ivity in hexagonal ferrites in lieu of conventional approaches such as cati onic doping.