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Self-propagating high-temperature synthesis of barium-chromium ferrites BaFe <inf>12-x</inf> Cr <inf>x</inf> O <inf>19</inf> (0 ≤ x ≤ 6.0)

Kuznetsov, MV; Fernandez Barquin, L; Pankhurst, QA; Parkin, IP; (1999) Self-propagating high-temperature synthesis of barium-chromium ferrites BaFe <inf>12-x</inf> Cr <inf>x</inf> O <inf>19</inf> (0 ≤ x ≤ 6.0). Journal of Physics D: Applied Physics , 32 (20) pp. 2590-2598. 10.1088/0022-3727/32/20/302.

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Abstract

Pure and chromium substituted barium ferrites BaFe 12-x Cr x O 19 (0 ≤ x ≤ 6.0) have been synthesised in air by self-propagating high-temperature synthesis (SHS): a combustion process involving a reaction of barium peroxide, iron oxide, chromium oxide and iron metal powder. Two series of SHS 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°C for 2 h. X-ray data showed that hexagonal ferrites were produced, and systematic changes in lattice parameters were seen as a function of the Cr content. Scanning electron microscopy indicated crystallites of order 1 μm. Energy dispersive x-ray analysis (EDAX) showed that the samples were homogeneous with the expected Ba:Fe:Cr ratios. Mossbauer, x-ray and magnetic hysteresis data showed a progressive change in the sublattice occupancy and magnetization with Cr content. Some differences in magnetic parameters were observed between series 1 and 2, implying that the use of a magnetic field during SHS can influence product microstructure. In particular, the coercive forces in the Cr doped ferrites showed maxima at x = 1.5 and x = 1.0 for series 1 and 2 respectively, with the series 2 coercivities being consistently 40-50% smaller than their series 1 counterparts. This indicates that applied field SHS provides an alternative route to reducing coercivity in hexagonal ferrites in lieu of conventional approaches such as cationic doping.

Type: Article
Title: Self-propagating high-temperature synthesis of barium-chromium ferrites BaFe <inf>12-x</inf> Cr <inf>x</inf> O <inf>19</inf> (0 ≤ x ≤ 6.0)
DOI: 10.1088/0022-3727/32/20/302
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > MAPS Faculty Office
URI: http://discovery.ucl.ac.uk/id/eprint/31875
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