Mossbauer studies of the SrTiO₃: Fe⁵⁷ system

Abstract

Mossbauer studies of the SrTiO₃: Fe⁵⁷ system used as an absorber have shown that iron enters the SrTiO₃ lattice substitutionally at the Ti⁴⁺ site in its high-spin ferric state and is usually associated with a charge-compensating oxygen vacancy in agreement with the EPR evidence. On firing these samples in hydrogen, the quadrupole-split spectrum of Fe³⁺ associated with an oxygen vacancy transforms into a zeeman-split spectrum with hf field and isomer shift characteristic of iron metal, indicating the formation of colloidal iron. Vacuum firing of the original air-fired samples tends to convert part of the Fe³⁺ ions into Fe²⁺ through the creation of more oxygen vacancies. The stages through which atomically dispersed Fe³⁺ ions are converted into colloidal iron on hydrogen firing and vice versa have been indicated.