STRUCTURAL STUDY OF P4W14O50, A NEW ODD MEMBER IN THE SERIES (PO2)(4)(WO3)(2M)

摘要

Single crystals of the odd member m = 7 of the series of low dimensional tungsten bronzes (PO2)(4) (WO3)(2m) have been grown by means of chemical vapor transport technique. The structure has been solved from X-ray diffraction data in the monoclinic space group P2(1) with the lattice parameters a = 5.291(1) Angstrom, b = 6.557(2) Angstrom, c = 26.654(8) Angstrom, and beta = 90.19 degrees. In contrast to the m = 5 compound whose structure has been found as corresponding to the regular intergrowth of the two even members m = 4 and m = 6, the m = 7 compound can be considered as a pure phase whose structure is similar to that of m = 4, 6, or 8 members. It can indeed be described by a stacking of WO6 octahedral slabs of ReO3-type, all of the same thickness, connected through PO4 tetrahedra. The difference about the crystal symmetry between the terms m = 7 and m = 6 is discussed in terms of tilting of WO6 octahedra. (C) 1996 Academic Press, Inc. [References: 36]