Homogeneous solid-solution formation in Fe2O3-Al2O3 system observed by TEM, XAFS, and Mossbauer spectroscopy

We have characterized the mechanically alloyed (Fe2O3)1-x(Al2O3)x solid solution with corundum-type structure by means of TEM, EXAFS, and Mo center dot ssbauer spectroscopy emphasizing the homogeneity of cation distribution and the variation of magnetic property with the composition. HR-TEM revealed that the typical crystallite size of the solid solution is 10-20 nm and the observed lattice spacing is consistent with that evaluated from Vegard's law. EXAFS measurements showed that the radial distribution at Fe-Fe distance decreases monotonously with aluminum substitution, while Fe-O is not largely altered. Mo center dot ssbauer spectroscopy showed a gradual change in spectra from sextet peaks at x = 0 into doublet with increasing Al2O3 concentration up to x = 0.67, indicating that spin interaction is diluted by the homogeneous substitution of aluminum ions over the wide compositional range keeping corundum-type structure.