Preparation, characterization and sintering behavior of spherical iron oxide doped alumina particles

A continuous procedure for the preparation of homogeneous iron oxide doped alumina spherical particles is described. The method is based on the hydrolysis with ammonium hydroxide of liquid aerosols formed by spraying iron and aluminum nitrate aqueous solutions. The powder consisted of, according to X-ray diffraction and infrared spectroscopy, boehmite of low crystallinity. Heating of the as-prepared boehmite powders produced a series of transition aluminas that finally transform into the thermodynamically stable phase (alpha-Al2O3). It has been found that the temperature of such a transformation is lowered as iron oxide content in samples increases. Densification studies have shown that the presence of iron oxide has a beneficial effect on the sintering behavior of compacted powders. Thus, undoped samples did not achieve full density even after heating for 2 h at temperatures as high as 1500degreesC. In contrast, with 4 wt% iron oxide content full density microstructures, consisting of uniform equiaxed grains, were achieved after heating for 2 h at 1350degreesC. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.