Liquid-feed flame spray pyrolysis (LF-FSP) has been used to synthesize mixed-metal nanopowders in the (MgO)x(Fe2O3)1-x system from metalloorganic precursors. Iron propionate [Fe(O2CCH2CH3)3] and magnesium acetylacetonate [Mg(C5H7O2)2·2H2O] precursors were dissolved in ethanol, aerosolized with oxygen and combusted at temperatures > 1500 oC and thereafter quenched rapidly. The rate of nanopowder production was 30 g/h. The resulting nanopowders were collected in electrostatic precipitators, were un-aggregated with average particle sizes (APSs) < 45 nm and with specific surface areas (SSAs) of 40- 65 m2/g as determined from both the SSAs and X-ray line broadening analyses. Powders with a range of compositions (x = 0.30, 0.45, 0.50, 0.65, 0.75 and 0.90 ± 0.02) were characterized by XRD, BET, SEM, EDS, FTIR, and TGA-DTA. Particle sizes generally increased as the fraction of MgO increased and a single-phase spinel was observed over the range x = 0.30 and 0.65 with the two extremes lying about 15 mol% outside of the published thermodynamic spinel phase boundaries.

Keywords: Liquid-Feed Flame spray pyrolysis, nano-magnesioferrite, off-stoichiometric spinel.