By utilizing multifrequency electron paramagnetic resonance spectroscopy, the Fe functional center in the Fe3+-modified polycrystalline zirconate was studied. The single-phase polycrystalline sample remained orthorhombic and antiferroelectric down to 20K; as confirmed by high-resolution synchrotron powder diffraction. The Fe3+ ions were identified as substituting for Zr4+ at the B-site of the perovskite ABO3 lattice. As found for Fe3+:PbTiO3, the value of the fine-structure parameter, B20, was only consistent with a model in which a charged (FeZr’–VO▪▪)▪ defect associate was formed. In contrast to a well-defined Fe functional center in PbTiO3 with fine-structure parameters exhibiting variances of less than 3%, a strong broadening of the electron paramagnetic resonance powder pattern was observed in lead zirconate, indicating a much larger variance of fine-structure parameters. It was suggested that the apparent broad distribution of fine-structure parameters arose from the system's capability to realize different O vacancy positions in the first coordination shell around the Fe site. This proposed model of a small number of distinct Fe-O vacancy sites was supported by the observation that corresponding B20 and orthorhombic B22 fine-structure parameters of these sites were anticorrelated, a property not expected for random distributions of fine-structure parameters.

Iron-Oxygen Vacancy Defect Association in Polycrystalline Iron-Modified PbZrO3 Antiferroelectrics - Multifrequency Electron Paramagnetic Resonance and Newman Superposition Model Analysis. H.Meštrić, R.A.Eichel, K.P.Dinse, A.Ozarowski, J.van Tol, L.C.Brunel, H.Kungl, M.J.Hoffmann, K.A.Schönau, M.Knapp, H.Fuess: Physical Review B, 2006, 73[18], 184105 (10pp)