材料期刊网

The optical absorption and EPR spectra of Fe3+ impurity ions doped in near stoichiometric LiNbO3 crystal are studied by diagonalizing the complete energy matrices for a d(5) configuration ion in a trigonal ligand-field. By analyzing the optical absorption and EPR spectra simultaneously, the distortion parameters Delta theta(1) = 3.42 degrees, Delta theta(2) = -7.22 degrees are determined for Li+ substitutional position supported by ENDOR experiments. The theoretical results indicate that there exists a compressed distortion in LiNbO3:Fe3+ system, which may be ascribed to the fact that the radius of Fe3+ ion is slightly smaller than that of the host ion. Meanwhile, the local structure parameters R-1 = 2.08A, R-2 = 1.91A, theta(1) = 47.99 degrees and theta(2) = 62.52 degrees for the octahedral Fe3+ center in LiNbO3 crystal are also determined, which are close to that of the alpha Fe2O3. The calculated transition energies of octahedral Fe3+ center in LiNbO3 are in good agreement with those of Fe3+ cations in other oxides due to the similar octahedral (FeO6)(9-) cluster. (c) 2006 Elsevier B.V. All rights reserved.