Synthesis, crystal structures and ionic conductivities of Bi{sub 14}P{sub 4}O{sub 31} and Bi{sub 50}V{sub 4}O{sub 85}. Two members of the series Bi{sub 18-4m}M{sub 4m}O{sub 27+4m} (M=P, V) related to the fluorite-type structure
- Institut de Chimie de la Matiere Condensee de Bordeaux (ICMCB), UPR9048 CNRS, Universite de Bordeaux 1, 87 Avenue du Docteur A. Schweitzer, Pessac Cedex 33608 (France)
The two hitherto unknown compounds Bi{sub 14}P{sub 4}O{sub 31} and Bi{sub 50}V{sub 4}O{sub 85} were prepared by the direct solid-state reaction of Bi{sub 2}O{sub 3} and (NH{sub 4})H{sub 2}PO{sub 4} or V{sub 2}O{sub 5}, respectively. Bi{sub 14}P{sub 4}O{sub 31} crystallizes in a C-centred monoclinic symmetry (C2/c space group) with the unit-cell parameters: a=19.2745(2)A, b=11.3698(1)A, c=52.4082(2)A and {beta}=93.63(1){sup o} (Z=16). The symmetry of Bi{sub 50}V{sub 4}O{sub 85} is also monoclinic (I2/m space group) with lattice parameters of a=11.8123(3)A, b=11.7425(2)A, c=16.5396(2)A and {beta}=90.14(1){sup o} (Z=2). Both structures correspond to a fluorite-type superstructure where the Bi and P or V atoms are ordered in the framework. An idealized structural model is proposed where the structures result of the stacking of mixed atomic layers of composition [Bi{sub 14}M{sub 4}O{sub 31}] and [Bi{sub 18}O{sub 27}] respectively. This new family can be formulated Bi{sub 18-4m}M{sub 4m}O{sub 27+4m} with M=P, V and where the parameter m (0=<m=<1) represents the ratio of the number of [Bi{sub 14}M{sub 4}O{sub 31}] layers to the total number of layers in the sequence. Bi{sub 14}P{sub 4}O{sub 31} corresponds to m=1 when Bi{sub 50}V{sub 8}O{sub 85} corresponds to m=1/3. In this last case, the structural sequence is simply one [Bi{sub 14}V{sub 4}O{sub 31}] layer to two [Bi{sub 18}O{sub 27}] layers. As predicted by the proposed structural building principle, Bi{sub 14}P{sub 4}O{sub 31} is not a good ionic conductor. The conductivity at 650 deg. C is 4 orders of magnitude lower from those found in Bi{sub 46}M{sub 8}O{sub 89} (M=P, V) (m=2/3) and Bi{sub 50}V{sub 4}O{sub 85} (m=1/3)
- OSTI ID:
- 20725992
- Journal Information:
- Journal of Solid State Chemistry, Vol. 178, Issue 6; Other Information: DOI: 10.1016/j.jssc.2005.03.048; PII: S0022-4596(05)00148-9; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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