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Synthesis and Microstructural Characterisation of Two New One‐Dimensional Members of the (A 3 NiMnO 6 ) α (A 3 Mn 3 O 9 ) β Homologous Series (A = Ba, Sr)
Author(s) -
Hernando María,
Boulahya Khalid,
Parras Marina,
GonzálezCalbet Jose M.,
Amador Ulises
Publication year - 2003
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200300028
Subject(s) - octahedron , crystallography , chemistry , polyhedron , manganese , hexagonal prism , tetrahedron , triangular prism , trigonal prismatic molecular geometry , trigonal crystal system , prism , hexagonal crystal system , crystal structure , geometry , physics , mathematics , organic chemistry , optics
Two new members of the one‐dimensional (A 3 NiMnO 6 ) α (A 3 Mn 3 O 9 ) β homologous series, with the compositions (Sr 0.75 Ba 0.25 ) 5 NiMn 3 O 12 and Sr 9 Ni 2 Mn 5 O 21 , have been synthesised. Their structures can each be described as a hexagonal array of infinite one‐dimensional chains of face‐sharing polyhedra, running parallel to the c axis and separated by the Sr/Ba cations. The structure of (Sr 0.75 Ba 0.25 ) 5 NiMn 3 O 12 , which constitutes the (α = 3, β = 2) member of the series, is made up of three face‐sharing octahedra linked by one trigonal prism. For Sr 9 Ni 2 Mn 5 O 21 (α = 2, β = 1) the sequence of polyhedra along the chains corresponds to a motif consisting of two octahedra−one trigonal prism−three octahedra−one trigonal prism. The manganese atoms occupy the octahedral sites in both phases, while the Ni 2+ cations are distributed in the trigonal‐prismatic sites in a disordered way. Only a small fraction of these (close to 20%) is located at the centres of the trigonal prisms, 80% being displaced towards the rectangular faces of the polyhedra and giving rise to a square‐planar‐like coordination. Both oxides present twinned microstructures, as evidenced by SAED and HREM. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)