材料期刊网

A simple displacement scheme is proposed in the case of charge misfitting substitution for 3d(5) ions in corundum-type structures. According to the scheme, the impurity ion does not occupy the exact site of the host ion, but is displaced along the C-3 axis. The displacement direction depends upon the change of the electrostatic repulsive force between the cationic pair and hence upon the charge carried by impurity ion. Based on this, the zero-field splittings of MgTiO3:Fe3+ and Al2O3:Mn2+ crystals are reasonably explained and the substitution positions of Fe3+ and Mn2+ ions in LiNbO3 crystals are determined from the superposition model calculations. The results show good agreement with those obtained from other experiments.