HREM: a Useful Tool to Formulate New Members of the Wide Bi3+\M2+ Oxide Phosphate Series

A number of double Bi3+\M2+ oxide phosphates have been isolated and structurally described using variable arrangements of isolated [Bi-M-O]n+ polycations surrounded by PO4 groups. The relationship between them leads to suspecting a great number of new arrangements within new compounds. In this work, the use of electron diffraction associated with high resolution imaging has considerably facilitated the prospecting. On the basis of the strong contrast observed by HREM between polycations of variable width and the inter-space, a high-resolution image code and formulation rules have been established. This has allowed the formulation of original compounds, first detected in multiphased samples, yielding the synthesis of single-phased materials essential for the structural and physical characterization. This paper illustrates the complementarity between X-ray diffraction and electron microscopy studies to be especially well suited in this family of materials.