Bi3+/M2+ Oxyphosphate: A Continuous Series of Polycationic Species from the 1D Single Chain to the 2D Planes. Part 2: Crystal Structure of Three Original Structural Types Showing a Combination of New Ribbonlike Polycations
2006-08-21T00:00:00Z (GMT) by
With the assistance of structural models deduced from the high-resolution electron microscope (HREM) investigation presented in Part 1 of this work, three new structural types were pointed out in Bi2O3−MO−P2O5 ternary systems. Their crystal structures are built on the arrangement of 2D polycationic ribbons formed of edge-sharing O(Bi,M)4 tetrahedra and isolated by PO4 groups. Prior to this study, materials with ribbons up to n = 3 tetrahedra wide have been discovered. The original structures presented here display longer n = 4−6 cases, which suggests a possible continuous series of polycationic entities that range from the single chain (one tetrahedron wide) to the infinite [Bi2O2]2+ Aurivillius layer. The ribbons with n > 3 show strong structural modifications that are able to bring a good ribbon−phosphate cohesion. In addition to these fascinating structural results, this work fully confirms the validity of the decoding established from HREM images of a single crystallite in inhomogeneous mixtures.