Preparation of LaFe12ONO19 by coprecipitation method to reduce the sintering time

LaFe12ONO19 was synthesised by the coprecipitation method. The preparation involved the precipitation of the metal ions from a nitrate solution in the presence of ammonium hydroxide, followed by a digestion step at 80°C. The La:Fe ratio was fixed at 1:8 in order to compensate La losses. The precipitated powder was carefully washed, filtered and dried prior to its oxidation at 800°C for 24 hours. Pressed samples were annealed at several temperatures and times, and rapidly quenched to preserve the LaFe12ONO19 phase. The study of the annealing temperature revealed a shift of the stability range to lower temperatures. 1375°C was fixed to find the influence of the sintering time over the La hexaferrite formation. The sintering time required to obtain La hexaferrite was found to be as short as 5 minutes, which is significantly lower than the one reported before (24–29 hours); however, the highest saturation magnetisation was obtained at 8 hours.