XAS study of lanthanum coordination environments in glasses of the system K2OSiO2La2O3

E. M. Larson, A. J.G. Ellison, F. W. Lytle, A. Navrotsky, R. B. Greegor, J. Wong

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31 Scopus citations

Abstract

The La L1 and L3 XANES and L3 EXAFS have been investigated for the series of glasses 10K2O50SiO2x La2O3 (x = 1, 5, 10) and (10 - x)K2O40SiO2-(x/3)La2O3 (x = 7.5, 5, 2.5) and model compounds La2O3, LaAlO3, LaPO4, La2NiO4, La2CuO4 and La(OH)3. An edge resonance at ∼ 25 eV above the L1 edge in the glass spectra is concentration-dependent, decreasing in intensity with increasing lanthanum concentration. The 2s → nd forbidden transition increases with La2O3 concentration, indicating a reduction in the 'average' site symmetry of the first coordination shell of La. Mapping X(k) space, which is a new and promising technique, was employed to extract bond distance, coordination number and thermal parameters from the EXAFS. By this method, one calculates the complete X(k) space a function of all physically reasonable values of the adjusted parameters in all possible combinations. The advantage in this method is the assurance of a global minimum. Bond lengths were comparable to those obtained by Fourier transforming the phase corrected EXAFS. The values are 2.42 Å (± 0.03 A ̊) for LaO. The coordination numbers (N ≤ 7 ± 1.5) were derived by mapping and comparison to the published structures for other La compounds. X(k) mapping is compared with least-squares fitting the data, and the correlation between the Debye-Waller factor and coordination number is also discussed.

Original languageEnglish (US)
Pages (from-to)260-272
Number of pages13
JournalJournal of Non-Crystalline Solids
Volume130
Issue number3
DOIs
StatePublished - Aug 1991
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Materials Chemistry

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