Stairlike Aurivillius Phases in the Pseudobinary Bi5 Nb3 O15 -ABi2 Nb2 O9 (A = Ba and Sr) System: A Comprehensive Analysis Using Superspace Group Formalism

Inorganic Chemistry
Gwladys SteciukPhilippe Boullay

Abstract

We report the possibility of extending the so-called stairlike Aurivilius phases in the pseudobinary Bi5Nb3O15-ABi2Nb2O9(A = Ba and Sr) over a wide range of compositions. These phases are characterized by a discontinuous stacking of [Bi2O2] slabs and perovskite blocks, leading to long-period intergrowths stabilized as a single phase. When analyses from precession electron diffraction tomography and X-ray and neutron powder diffraction are combined, the monoclinic incommensurately modulated structure with q = αa* + γc* previously proposed for the ABi7Nb5O24composition could be generalized to the Bi5Nb3O15-ABi2Nb2O9(A = Ba and Sr) compounds. Considering the compositions expressed as (A,Bi)1- xNbxO3-3 x, the stacking sequence associated with compositions ranging from x =2/5to3/8is governed by the component γ of the modulation vector and can be predicted following a Farey tree hierarchy independently to the A cation. The length of the steps, characteristic of the stairlike nature, is controlled by the α component and depends on the substitution ratio A/Bi and the nature of A (A = Ba and Sr). This study highlights the compositional flexibility of stairlike Aurivillius phases.

References

Nov 24, 2011·Chemical Reviews·Anna KubackaGerardo Colón
Dec 3, 2014·Acta Crystallographica Section B, Structural Science, Crystal Engineering and Materials·Shmuel SamuhaLouisa Meshi
Mar 3, 2015·Acta Crystallographica. Section A, Foundations and Advances·Lukáš PalatinusCinthia Antunes Corrêa
Dec 5, 2015·Acta Crystallographica Section B, Structural Science, Crystal Engineering and Materials·Lukáš PalatinusVáclav Petříček

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