2015-Sustainable Industrial Processing Summit
SIPS 2015 Volume 7: Ionic Liquids & Energy Production
| Editors: | Kongoli F, Gaune-Escard M, Mauntz M, Rubinstein J, Dodds H.L. |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2015 |
| Pages: | 310 pages |
| ISBN: | 978-1-987820-30-0 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Inorganic Fluorides Analysed by XPS
Miroslav Boca1; Jarmila Mlynarikova1; Blanka Kubikova1;1INSTITUTE OF INORGANIC CHEMISTRY SAS, Bratislava, Slovakia (Slovak Republic);
Type of Paper: Regular
Id Paper: 62
Topic: 13
Abstract:
Molten salt method that is frequently used for preparation of different materials or pure compound at high temperatures, suffers with one unfavourable but principal complication. When particular phases are mixed and melted, some reaction usually takes place and consequent cooling provides product of these chemical or physical processes. The reaction product, however, usually contains impurities that arise either from i) starting components or ii) competitive reactions. Both major and minor phases are either known and fully structurally characterized, or their stoichiometry is believed to be known based on only XRD. The following complications may arise: i) phase characterized by only XRD may happen to be shown as incorrect ii) the unknown phase is present and its composition could be estimated based on isostructural properties, iii) the amount of the phase is below detection limit of XRD and remains unrevealed.
X-ray photoelectron spectroscopy could reveal the presence of low concentration phases, as unreacted reactants or product of competitive reactions because the detection limit of this spectroscopy is much lower. Moreover, some important information about the structural properties can be retrieved from surface of studied samples.
X-ray photoelectron spectroscopy was applied for identification of differently bonded fluorine atoms in series of compounds NaF, K2TaF7, K3TaF8, K2ZrF6, Na7Zr6F31 and K3ZrF7. Three different types of fluorine atoms were described qualitatively and quantitatively. Uncoordinated fluorine atoms (F-) provide signals at lowest binding energies, followed by signals from terminally coordinated fluorine atoms (M-F) and then bridging fluorine atoms (M-F-M) at highest energy. Based on XPS signals assigned to fluorine atoms in compounds with correctly determined structure it was suggested that fluorine atoms in K3ZrF7 have partially bridging character.
In the second example, the series of the phases KTaF6, K2TaF7, K3TaF8 vs KNbF6, K2NbF7 and K3NbF8, correlation of XPS data was performed.