High-frequency electron paramagnetic resonance investigation of the Fe3+   impurity center in polycrystalline PbTiO3 in its ferroelectric phase
  The intrinsic iron(III) impurity center in polycrystalline lead titanate was investigated by means of high-frequency electron paramagnetic resonance (EPR) spectroscopy in order to determine the local-environment sensitive fine structure parameter D. At a spectrometer frequency of 190 GHz, spectral analysis of a powder sample was unambiguously possible. The observed mean value D = +35.28 GHz can be rationalized if Fe3+ ions substitute for Ti4+ at the B-site of the perovskite ABO3 lattice forming a directly coordinated iron - oxygen vacancy defect associate. A consistent fit of the multi-frequency data necessitated use of a distribution of D values with a variance of about 1 GHz. This statistical distribution of values is probably related to more distant defects and vacancies. 
Hrvoje Mestric, Ruediger-A. Eichel, Klaus-P. Dinse, Andrew Ozarowski,   Johan van Tol, Louis Claude Brunel