FERRITE BI(13)BA(2)SR(25)FE(13)O66 - A DOUBLE COLLAPSED STRUCTURE DERIVED FROM THE 2201-0201 INTERGROWTH BI2SR4FE2O10

摘要

A new ferrite, Bi13Ba2Sr25Fe13O66, has been synthesized. It crystallizes in the space group C2/c with a = 39.108 (5) Angstrom, b = 5.4371 (5) Angstrom, c = 37.223 (5) Angstrom, beta = 114.9 degrees (1). A structural model has been established, using high-resolution electron microscopy. It can be described as a double collapsed structure derived from the ''2201-0201'' intergrowth Bi2Sr4Fe2O10. Another description of this structure is presented: it consists of stair-like Bi2O2 layers parallel to (001) intergrown with K2NiF4-type layers. The stairs that form the bismuth oxygen layers are 7 bismuth atoms wide, whereas the K2NiF4 layers are 13 FeO6 octahedra thick, so that this structure can be considered as the ''m = 7, n = 13'' members of a very promising series of ferrites (Bi2-xBaxO2)(m) (Sr2-xBaxFeO4)(n). Extended defects involving longitudinal intergrowth of two m and m' members are observed, as well as antiphase boundaries and ''SrO'' intergrowths. (C) 1995 Academic Press,Inc. [References: 14]