Investigation of the Alkali-Metal Vanadium Oxide Xerogel Bronzes: AαV2O5.nH2O (A = K and Cs)

Y. J. Liu, J. A. Cowen, T. A. Kaplan, D. C. DeGroot, J. Schindler, C. R. Kannewurf, M. G. Kanatzidis

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Abstract

The synthesis of bronze-like AxV2O5·nH2O xerogels (A = K and Cs, 0.05 < x < 0.6) and systematic characterization of their chemical, structural, spectroscopic magnetic, and chargetransport properties are reported. These materials were prepared by the reaction of V2O5·nH2O with various amounts of alkali iodide (KI and CSI) in acetone under N2 atmosphere for 3 days. X-ray diffraction and spectroscopic data indicate that the V2O5 framework in AxV2O5·nH2O maintains the pristine V2O5 xerogel structure. The increased V4+ (d1) concentration in the V2O5 framework causes the disappearance of EPR hyperfine structure and the increase of magnetic susceptibility and electrical conductivity. The optical diffuse reflectance spectra of these compounds show characteristic absorption bands due to inter-valence (V4+/V5+) charge-transfer transitions. The magnetic behavior is best described as Curie-Weiss type coupled with temperature-independent paramagnetism (TIP). The Curie constant and EPR peak width of the AxV2O5·nH2O materials show unusual behavior consistent with strong antiferromagnetic coupling of neighboring V4+ centers. The electrical conductivity slightly increases with V4+ concentration, and its temperature dependence indicates a thermally activated process. The thermoelectric power of the AxV2O5·nH2O materials is negative and becomes less negative with increasing V4+ concentration (i.e., increasing x).

Original languageEnglish
Pages (from-to)1616-1624
Number of pages9
JournalChemistry of Materials
Volume7
Issue number9
DOIs
Publication statusPublished - Sep 1995

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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    Liu, Y. J., Cowen, J. A., Kaplan, T. A., DeGroot, D. C., Schindler, J., Kannewurf, C. R., & Kanatzidis, M. G. (1995). Investigation of the Alkali-Metal Vanadium Oxide Xerogel Bronzes: AαV2O5.nH2O (A = K and Cs). Chemistry of Materials, 7(9), 1616-1624. https://doi.org/10.1021/cm00057a007