Nonstoichiometry and defect structure of Mn-doped BaTiO3−δ

Oxygen nonstoichiometry (δ) of 1 m/o Mn-doped polycrystalline BaTiO3−δ has been measured as a function of oxygen partial pressure in the range of 10−16≤PO2/atm≤0.1 at elevated temperatures (900≤T/°C≤1100) by a solid-state coulometric titration technique. The extent of nonstoichiometry of Mn-doped BaTiO3 is much larger than that of undoped BaTiO3, which is attributed to defect-chemical role of Mn as acceptors. The nonstoichiometry isotherms indicate that Mn-ions change their valence from +4 (or MnTix) to +3 (or MnTi′) to +2 (or MnTi″) with decreasing PO2.