Structure resolution by electron diffraction tomography of the complex layered iron-rich Fe-2234-type Sr5Fe6O15.4

The crystal structure of the strontium ferrite Sr5Fe6O15.4, was solved by direct methods on electron diffraction tomography data acquired on a transmission electron microscope. The refined cell parameters are a=27.4047(3)Å, b=5.48590(7)Å and c=42.7442(4)Å in Fm2m symmetry. Its structure is built up from the intergrowth sequence between a quadruple perovskite-type layer with a complex rock-salt (RS)-type block. In the latter iron atoms are found in two different environments : tetragonal pyramid and tetrahedron. The structural model was refined by Rietveld method based on the powder X-ray diffraction pattern.