Modulated structure ofBa6ZnIr4O15; a comparison withBa6CuIr4O15 andSrMn1-xCoxO3-y

Journal of Materials Chemistry (Impact Factor: 5.97). 01/1997; 7(8):1559-1564. DOI: 10.1039/A700964J

ABSTRACT The new phase Ba6CuIr4O15 has been shown by powder X-ray diffraction to be a member of the perovskite-related structural family A3n+3A'nBn+3O6n+9 with n=1; space group R32, a=10.1196(3), c=13.4097(4) Å. The trigonal-prismatic A' sites and the octahedral B sites are both occupied by a disordered distribution of Ir and Cu. A combination of electron microscopy and X-ray diffraction has shown that Ba6ZnIr4O15 has a related incommensurate structure with a≈10.1, c≈4.4 Å and a modulation vector q=a*+0.35c*. Alternatively, Ba6ZnIr4O15 can be considered as a composite of trigonal (cell 1) and rhombohedral (cell 2) substructures with a1=a2=10.1228(9) c1=4.4099(6), c2=2.6982(2) Å. It is shown that the same structural formalism can be used to describe the incommensurate hexagonal phase of SrMn1−xCoxO3−y.

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