Building 3D materials from adjustable 2D-units; towards the Design of new Bi-based compounds
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Building 3D materials from adjustable 2D-units; towards the Design of new Bi-based compounds. M. Colmont1, D. Endara1, M. Huvé1, S.V. Krivovichev2, O. Mentré1 1
Unité de Catalyse et de Chimie du Solide, UMR 8181, bât C7, 59652 Villeneuve d'Ascq cedex, France, 2 Department of Crystallography, St. Petersburg State University, University Emb. 7/9, St. Petersburg 199034, Russia
ABSTRACT In the Bi2O3-MO-P2O5 diagram, on the basis of previous compounds based on 2D-ribbon like units, we have predicted and prepared the infinite term. It contains [Bi2O2]2+ planes arranged within a never-observed crystallographic form. In this series, the ribbons-like units are polycations built on the linkage of n O(Bi,M)4 tetrahedra along their width and infinite in a perpendicular dimension. Hence, this novel form completes the continuous series of analogue compounds, whose building units now extend from the single chain to the infinite plane, via a number of discrete n values (2,3,4,5,6,7,8,9,10,11). The presented materials of formulae Bi4MP2O12 (M= Zn and Mg) roughly show the same crystal structure. However different arrangements of the groups located between the [Bi2O2]2+ planes are at the origin of a complex superstructure in the case of the zinc compounds. INTRODUCTION The predictable approach and rational design of new compounds is nowadays a major challenge in solid-state chemistry. The concept of secondary building units (SBU) showed its efficiency, especially concerning the achievement of new open-metal oxide framework compounds in the field of new hybrid compoundsi. In such a way, the coherence between the units is simplified by the combined use of an inorganic part complexed by organic ligands, forming an inorganic-organic framework. Parallel to these hybrid compounds, the engineering of new “pure” inorganic remains a rare science. A procedure to success in the design of new materials is the use of phase homologiesii, especially in the case of prediction of new phases with predictable composition and structure. This powerful approach is interesting to designing new inorganic solid state compounds and precisely when filiations between different compounds can be evidenced. This non conventional approach has been applied to the synthesis of new Bi-based phosphate compounds. Indeed, the Bi2O3-MO-P2O5 ternary system is known to be rich and a number of inorganic structural types have already been isolatediii . To establish the structural relationships between them, and in order to prepare new polytypes, a “Lego game” based on Building Units (BU), which obey structural rules, has been rationalized. The convenient
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description of these structures (in order to distinguish the BUs) is based on the anti-structure approach. i.e. the BUs are formed from the association of O(Bi,M)4 tetrahedra sharing edges to built ribbons of variable width, from n=1, 2, ..., 11iv. These ribbons are surrounded by isolated PO4 groups which number is related to their n-sizes, as already established in a previous paper. In some cases, channels are created
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