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Structure study of Bi2.5Na0.5Ta2O9 and B2.5Nam-1.5NbmO3m+3 (m=2-4) by neutron powder diffraction and electron microscopy

Författare

Summary, in English

The crystal structures of Bi2.5Na0.5Ta2O9 and Bi2.5Nam-1.5NbmO3m+3 (m = 3,4) have been investigated.ysis of their neutron powder diffraction by the Rietveld anal patterns (lambda = 1.470 Angstrom). These compounds belong to the Aurivillius phase family and are built up by (Bi2O2)(2+) fluorite layers and (A(m-1)BnO(3m+1))(2-) (m = 2-4) pseudo-perovskite slabs. Bi2.5Na0.5Ta2O9 (m = 2) and Bi2.5Na2.5Nb4O15 (m = 4) crystallize in the orthorhombic space group A2(1)am, Z = 4, with lattice constants of a = 5.4763(4), b = 5.4478(4), c 24.9710 (15) and a = 5.5095(5), b = 5.4783(5), c = 40.553(3) Angstrom, respectively. Bi2.5Na1.5Nb3O12 (m = 3) has been refined in the orthorhombic space group B2cb, Z = 4, with the unit-cell parameters a = 5.5024(7), b = 5.4622(7), and c = 32.735(4) Angstrom. In comparison with its isostructural Nb analogue, the structure of Bi2.5Na0.5Ta2O9 is less distorted and bond valence sum calculations indicate that the Ta-O bonds are somewhat stronger than the Nb-O bonds. The cell parameters a and h increase with increasing m for the compounds Bi2.5Nam-1.5NbmO3m+3 (m = 2-4), causing a greater strain in the structure. Electron microscopy studies verify that the intergrowth of mixed perovskite layers, caused by stacking faults, also increases with increasing m. (C) 2002 Elsevier Science (USA).

Publiceringsår

2002

Språk

Engelska

Sidor

86-96

Publikation/Tidskrift/Serie

Journal of Solid State Chemistry

Volym

167

Issue

1

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Chemical Sciences

Nyckelord

  • Aurivillius phases
  • electron microscopy
  • Bi2.5Na0.5Ta2O9
  • B1.5Na0.5Nb2O9
  • Bi2.5Na2.5Nb4O15
  • bi(2.5)Na(1.5)Nb(3)O(12)
  • neutron powder diffraction

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 0022-4596