The electron paramagnetic resonance (EPR) spectra of BaTi 1− x Mn x O 3 ceramics powder (0.005≤ x ≤0.016) were studied in different frequency bands (9 and 34 GHz). In as-sintered and air-annealed samples two different, axially symmetric EPR spectra assigned to Mn 4+ ions are observed. The manganese impurities are substituted at Ti sites corresponding to the different distorted octahedra in the 3C and 6H modification of BaTiO 3 . The temperature dependence of these EPR spectra allowed the unambiguous assignment of the paramagnetic ions to the lattice site in cubic and hexagonal modification. After annealing the samples in reducing atmosphere a drastic change in the EPR spectra is observed. Only isolated Mn 2+ ions and associates consisting of Mn 2+ ions and oxygen vacancies in the 3C modification of BaTiO 3 are detected.
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Böttcher et al. (2005) studied this question.