SUBSTITUTION AND PROPERTIES OF BI PB-BASED FERRATES OF 3212-TYPE/

Bi-based ferrates of type 3212 with three rocksalt-like layers between the Fe containing perovskite slabs of general formula (Bi, Pb, Sr)3Sr 3Fe2O10+z are characterized by a hole concentration of about 0.25 h+/F e ion. According to investigations by XRD, SEM, EDXA, Mossbauer, magne tic, electrical, and vibrational spectroscopic measurements, charge de localization by hopping conduction is present at room temperature wher eas at low temperatures a transition to antiferromagnetism with charge localization takes place. Increase or decrease of positive charge by partial substitution La3+ --> Sr2+ or Pb2+ --> Bi3+ is simply compensa ted by an insertion or depletion of oxygen from the rocksalt layers an d no exchange of carriers between the perovskite slabs and the rocksal t layer is detectable.