Design of New Structural Types from Oxocentered Tetrahedra : Continuous Polycationic Series from 1D Chains to 2D Planes
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Design of New Structural Types from Oxocentered Tetrahedra : Continuous Polycationic Series from 1D Chains to 2D Planes in New Bismuth Compounds Mentre olivier, Colmont marie, and Huve marielle UCCS, villeneuve d'ascq, 59652, France
ABSTRACT In the Bi2O3-MO-P2O5 diagrams, most of the inorganic frameworks display Bi-M-O polycationic ribbons isolated by XO4 groups and interstitial cationic channels. They are formed of edge sharing O(Bi,M)4 tetrahedra. The width of the ribbons coexisting in the structures and their arrangement is changed from one compound to the next one. Due to mixed Bi3+/M2+ particular positions, a great chemical flexibility and a great degree of disorder may exist. It has been possible to extend ribbons to infinite [Bi2O2]2+ like sheets, sandwiched between XO4 based layers. In addition to this fascinating continuous polymerization from 1D chains to 2D sheets, O(Bi,M)4 and XO4 groups form ideal structural units for the designing of new materials through empirical structural rules that has been established. INTRODUCTION The creative design of new crystalline inorganic oxide based compounds is ruled out by its descriptive aspect, i.e. the conception of a 3D edifice in term of building units. Then, for instance the well known versatile series of hexagonal perovskite compounds are generally described by the close packing of anionic layers. Therefore, all intermediate between the tridimensionnal 3CLaMnO3 type [1] and the monodimensional 2H-BaNiO3 type [2] can be viewed through the diversification of the stacking sequence. Then, the filling of octahedral interstices achieved the creation process of new materials. As a matter of fact, most of these possible structural types exist, even more extendable by the possibility of deficient layers generally yielding tetrahedral interstices [3]. This approach is all the more efficient in the field of 2D- layered compounds, in which modulable anionic and cationic slabs stack in the solid. For instance, in the Aurivillius series [Bi2O2]2+ layers are sandwiched between [An-1MnO3n+1]2- perovskite blocks of thickness n MO6 octahedra. Then the n = 1, 2 ,3 … can be artificially designed and have been effectively prepared in materials such as Bi2WO6 [4], Bi3NbTiO9 and Bi4Ti3O12 [5]. However, this prospecting aspect is limited in several cases dealing with complex arrangement of various MOy polyhedra, not well displaying a typical adaptative framework. In that case an alternating solution may be the description of the anti-phase structure, e.g. the packed array of cations into the interstices of which the anions are inserted [6]. Within this approach, new structural units are often evidenced and leads to the viewing of new structural archetypes. This work describes the design of new Bi-based oxo phosphates (vanadates, arsenates …) via the use of the anti-phase concept.
EXPERIMENT The different BiwMxOy(PO4)z oxides (M= Co, Cu, Cd, Zn…) reported in this work have been prepared by heating stoechiometric mixtures of Bi2O3, MO and (NH4)2HPO4. Several heating-grin
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