The role of different network modifying cations on the speciation of the Co2 + complex in silicates and implication in the investigation of historical glasses

Cristina Fornacelli, Andrea Ceglia, Susanna Bracci, Marcia Vilarigues

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

In the last decades the speciation of the cobalt complex in a glass matrix has been extensively studied. Bivalent cobalt ions in glasses of different composition commonly adopt a tetrahedral coordination, though hexa- or penta-coordinated species are also possible. Changes in the absorbance spectrum of Co-doped glasses were attested in previous studies according to the introduction of different modifying cations. A shifting of the first sub-band characterizing the typical triplets of tetrahedral Co2 + ions in both the visible and near infrared regions was observed, but discrepancies in literature suggested a relevant role of glass composition on the definition of the optical signature of cobalt. Co-doped glasses with different composition (soda-lime, potash-lime, mixed alkali and ZnO-Na2O-CaO-SiO2) were studied via Fiber Optic Reflectance Spectroscopy (FORS). Pseudo-Voigt functions were used for the deconvolution of the absorbance spectra and the features of the bands characteristic of each cobalt complex were investigated. The structural role played by each modifying cation and the fundamental implications of glass basicity on the speciation of different Co-complexes were stressed. Changes in glass structure resulted in different equilibria between the three absorbing species whose specific optical signatures in the 480–530 nm region interact to determine the resulting absorbance spectrum.

Original languageEnglish
Pages (from-to)507-515
Number of pages9
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Volume188
DOIs
Publication statusPublished - 5 Jan 2018

Keywords

  • Cobalt(II)
  • Coordination
  • FORS
  • Glass structure

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