PbMnO2.75—a high-pressure phase having a new type of crystallographic shear structure derived from perovskite

Bougerol, Catherine; Gorius, M.F.; Grey, Ian E.

doi:10.1016/s0022-4596(02)00065-8

Cited by 41 publications

(55 citation statements)

References 20 publications

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“…Tunnels are formed in that network because of an ordered arrangement of vacancies at the B sublattice. Under high pressure also the anion deficient compound Pb 0.9 MnO 2.63 with continuous quasi-2D perovskite blocks separated by planar interfaces is formed [4]. A displacement of the blocks with respect to each other over 1 /2[110] p occurs at the interfaces, which thus acquire crystallographic properties similar to those of the crystallographic shear (CS) planes in binary transition metal oxides.…”

Section: Introductionmentioning

confidence: 99%

New perovskite-based manganite Pb2Mn2O5

Hadermann

Abakumov

Perkisas

et al. 2010

Journal of Solid State Chemistry

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Section: Introductionmentioning

confidence: 99%

New perovskite-based manganite Pb2Mn2O5

Hadermann

Abakumov

Perkisas

et al. 2010

Journal of Solid State Chemistry

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“…Different complex structural phenomena concerning the anion sublattice of the perovskites were observed and studied with regard to their influence on the physical properties of the materials. Among them are the oxygen vacancy distribution, ordering and evolution [11][12][13] and the shear planes formation [14][15][16][17]. The local coordination of the B cation seems to play a crucial role for the magnetic and electric behavior of the phases with perovskite-type structure, but according to [2] and [18], the role of some particular ions in A-cation position is very important for the multiferroic properties.…”

Section: Introductionmentioning

confidence: 99%

Combustion assisted synthesis and characterization of Pb1.33Sr0.67−xBaxFe2O5 (0≤x≤0.67) perovskite-type materials

Tzvetkov

Petrova

Kovacheva

2009

Journal of Alloys and Compounds

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“…The [14] occur because the B cations are able to adopt coordination numbers of 5 or 6 and because the Pb 2+ cations, which have a lone electron pair, favor an asymmetric coordination environment. The Pb atoms within the six-sided channels of all three structures are coordinated to O atoms at three short (2.28-2.43 ) and three long (2.63-2.70 ) Pb À O distances.…”

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confidence: 99%

Crystallographic Shear Structures as a Route to Anion‐Deficient Perovskites

et al. 2006

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Because of the technological importance of perovskite-based oxides, numerous pathways towards new structures have been developed, including ordering at the A and/or B cation sites of the perovskite (ABO 3 ) structure, vacancy ordering at the anion site, the intergrowth of perovskite and related structures, and the formation of hexagonal perovskite polytypes. However, it has been generally accepted that crystallographic shear (CS) structures cannot be realized in perovskites.[1] CS planes commonly occur in anion-deficient oxides derived from the ReO 3 or rutile (TiO 2 ) structures, which are based on metal-centered octahedra. Arrangement of the CS planes at different periodicities generates a homologous series. Some of the well-known examples of CS structures are M n O 3nÀ1 , M n O 3nÀ2 (M = Mo, W), Ti n O 2nÀ1 , and the block structures of Nb 2 O 5 and its Ti-containing derivatives.[2-6] The shear operation is such that along the CS plane the octahedra share edges or faces, instead of corners or edges as in the basic structure. The ReO 3 structure is based on the same threedimensional framework of corner-sharing BO 6 octahedra found in the perovskite structure, but the 12-coordinate A cation sites of the perovskite structure are empty in ReO 3 . Usually, the presence of A cations in perovskites favors point defects in the anion sites (in a random or ordered arrangement), leading to a lower coordination number for the B cations, and prevents the elimination of anion point defects by a shear operation.[2] Herein, we report the occurrence of CS structures in perovskite-based "Pb 2 Fe 2 O 5 " for the first time. We also describe the general crystallographic mechanism of CS-plane formation in a perovskite framework with the A sites filled by cations bearing a lone 6s 2 electron pair, which involves the elimination of O vacancies by the shear operation and the relaxation of the structure at the CS plane.We discuss the role of the lone electron pair in directing structure formation, as well as the relationship between the crystallographic orientation of the CS plane and the chemical composition. The discovery of this mechanism opens up new possibilities for the design of novel perovskite-based compounds containing A cations with a lone 6s 2 electron pair. "Pb 2 Fe 2 O 5 " (or "PbFeO 2.5 ") is expected to be an aniondeficient perovskite of the brownmillerite (Ca 2 AlFeO 5 ) type; [7][8][9] however, its structure has not yet been determined. Because of the complexity of the structure and the prevalence of domain fragmentation, the only road to solving the structure is by transmission electron microscopy (TEM). The brighter reflections in the electron diffraction (ED) patterns of "Pb 2 Fe 2 O 5 " (Figure 1 a) reveal a perovskite sublattice with a parameter a p % 3.9 (p denotes the perovskite subcell). Linear arrays of satellite reflections associated with each basic reciprocal lattice node are typical for periodic CS planes. The displacement vector for the CS planes was deduced from the ED patterns as R = 1/2 [110] p + 1/ ...

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PbMnO2.75—a high-pressure phase having a new type of crystallographic shear structure derived from perovskite

Cited by 41 publications

References 20 publications

New perovskite-based manganite Pb2Mn2O5

New perovskite-based manganite Pb2Mn2O5

Combustion assisted synthesis and characterization of Pb1.33Sr0.67−xBaxFe2O5 (0≤x≤0.67) perovskite-type materials

Crystallographic Shear Structures as a Route to Anion‐Deficient Perovskites

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