Microdomain texture and microstructures of Fe⁴⁺-containing CaTi_0.4Fe_0.6O_3-δ

A study of the structure of Fe-1V CaTi0.4Fe0.6O3-delta is presented and compared to data on the Fe-III counterparts. The powder XRD pattern was dominated by a simple cubic perovskite unit cell;, however, some small peaks indicated an orthorhombic distortion. All peaks could be indexed using a space group analogous to the Fe-III phase Ca3TiFe2O8. From HRTEM the strong cubic peaks are well explained by the Superposition of three equivalent and mutually perpendicular orthorhombic unit cells. TEM analysis further revealed a microdomain structure consisting of disordered intergrowths of CaTiO3- and Ca3TiFe2O8-like phases. Mossbauer spectra show that ca. 4% of the Fe cations are in the 4+ oxidation state. Results suggest that the Fe 4+ cations are associated with octahedral coordination and hence are associated with the CaTiO3-like regions, transition regions between the CaTiO3- and Ca3TiFe2O8 intergrown phases and the domain boundaries. Structural models for the intergrowths are proposed based on HRTEM image simulations. (C) 2004 Elsevier Inc. All rights reserved.