A homologous series Pb<sub>2n+1</sub>Nb<sub>2n−1</sub>O<sub>7n−1</sub> studied by electron microscopy
Leroux, Ch.; Badeche, T.; Nihoul, G.; Richard, O.; van Tendeloo, G.; Leroux Ch.; Laboratoire Matériaux Multiphasés et Interfaces, Université de Toulon-Var, B.P. 132, 83957 La Garde Cedex, France; Badeche T.; Laboratoire Matériaux Multiphasés et Interfaces, Université de Toulon-Var, B.P. 132, 83957 La Garde Cedex, France; Nihoul G.; Laboratoire Matériaux Multiphasés et Interfaces, Université de Toulon-Var, B.P. 132, 83957 La Garde Cedex, France; Richard O.; EMAT, University of Antwerp (RUCA), Groenenborgerlaan 171, 2020 Antwerpen, Belgium; van Tendeloo G.; EMAT, University of Antwerp (RUCA), Groenenborgerlaan 171, 2020 Antwerpen, Belgium
Журнал:
The European Physical Journal Applied Physics
Дата:
1999
Аннотация:
The PbO–Nb<sub>2</sub>O<sub>5</sub> phase diagram has been investigated, using electron diffraction and high resolution electron microscopy (HREM), for [Pb]/[Nb] ratios between 1 and 1.25. Apart from the basic pyrochlore structure, different long period superstructures, forming a homologous series Pb<sub>2n+1</sub>Nb<sub>2n−1</sub>O<sub>7n−1</sub> based on the pyrochlore structure have been found. Members with n = 5, 7, 9, 11 have been observed and their structure determined based on electron diffraction and HREM. Image simulations allow studying the influence of cation and oxygen vacancies in the basic structure. Ordering of oxygen vacancies could be detected while no cation vacancies are observed. Deviations from the perfect structure and ordered stacking defects are discussed.
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