The synthesis of nanocrystalline YIG in an ammonium nitrate melt

Yttrium iron garnet particles were synthesized in two different ways: first, in an ammonium nitrate melt (ANM) and second, via a solid-state reaction (SSR) route. The structural and magnetic properties of the samples were compared using XRD, SEM and dc magnetization measurements. It was observed for the ANM technique that the phase formation of YIG starts at 1000 degrees C and then develops with increasing temperature and sintering times. The saturation magnetization, M(s), increases sharply with increasing annealing temperature and then saturates at around 23 emu g(-1) above 1100 degrees C, while the coercivity decreases due to the increasing particle size. An almost single-phase sample was obtained through ANM route by annealing for 2 h at 1300 degrees C, after which the YIG fraction in the SSR sample was only 0.34, with M(s) = 7.08 emu g(-1). The average particle sizes of the ANM samples were calculated using experimentally determined M(s) values. It appeared that they vary from the sub-micron to the micron range, depending on the sintering temperature, and this coincides with the values determined from the SEM micrographs. These samples have homogeneous structures, small grains, good magnetic properties, and do not contain massive agglomerates. Therefore, the synthesis of YIG via the ANM technique represents another alternative to the SSR route. (C) 2008 Elsevier B.V. All rights reserved.