J. Phys. IV France 07 (1997) C1-351-C1-352
Mössbauer Characteristics of the Nonstoichiometric Sr2LaFe3O8+δ Perovskite Obtained by Electrochemical OxidationA. Wattiaux, L. Fournès, F. Zhou, J.C. Grenier, M. Pouchard and J. Etourneau
Institut de Chimie de la Matière Condensée de Bordeaux, avenue du Dr. A. Schweitzer, 33608 Pessac cedex, France
The nonstoichiometry and the vacancy ordering in the perovskite Ca2LaFe3O8 has been investigated in previous works [1,2]. More recently, the occurrence of a large nonstoichiometric domain has been shown in the Sr2LaFe3O8+δ system . Thus, we have used a new "Chimie Douce" method : electrochemical oxidation which has been developped in our laboratory  for obtaining Sr2LaFe3O8.90 in alkaline medium. The starting material Sr2LaFe3O8 has been characterized by XRD, chemical analysis and Mössbauer spectroscopy. This compound contains only Fe3+. The Mössbauer spectroscopy reveals, in the oxidized phase, the occurrence of antiferromagnetic interaction below TN = 195 K with a good agreement with electric and magnetic measurements. At low temperature, the presence of two sextets can be explained in terms of a charge disproportionation :
2 Fe 4+ → Fe(4-λ)+ + Fe(4+λ)+ .
© EDP Sciences 1997