The valence change of Fe in BaTiO3 studied by Mössbauer effect and gravimetry

The valence states of Fe and the charge compensation by oxygen vacancies of Fe57-doped BaTiO3 are studied by the Mössbauer effect and gravimetry as a function of O2 partial pressure. By preparational and analytical effort, it is ensured that the dopant homogeneously substitutes Ti4+ in the BaTiO3 lattice (up to 1.2 mol% Fe). It is found that Fe3+ is mainly present and that after annealing in pure oxygen up to 30% of the dopant is converted to Fe4+ and that by annealing in hydrogen the valency changes to Fe2+. Combining the Mössbauer results with the weight change it is shown quantitatively that the charge deficiency of the dopant (Fe3+, Fe2+) is compensated by doubly ionized oxygen vacancies.