VAISHNAV, Shuchi, HANNON, Alex, BARNEY, Emma and BINGHAM, Paul (2020). Neutron diffraction and Raman studies of the incorporation of sulfate in silicate glasses. Journal of Physical Chemistry C, 124 (9), 5409-5424.
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Abstract
The oxidation state, coordination and local environment of sulphur in alkali silicate (R2O-SiO2; R= Na, Li) and alkali-alkaline earth silicate (Na2O-MO-SiO2; M= Ca, Ba) glasses have been investigated using neutron diffraction and Raman spectroscopy. With analyses of both the individual total neutron correlation functions, and of suitable doped-undoped differences, the S-O bonds and (O-O)S correlations were clearly isolated from the other overlapping correlations due to Si-O and (O-O)Si distances in the SiO4 tetrahedra, and the modifier-oxygen (R-O and M-O) distances. Clear evidence was obtained that the sulphur is present as SO4 2- groups, confirmed by the observation in the Raman spectra of the symmetric S-O stretch mode of SO4 2- groups. The modifier-oxygen bond length distributions were deconvoluted from the neutron correlation functions by fitting. The Na-O and Li-O bond length distributions were clearly asymmetric, whereas no evidence was obtained for asymmetry of the Ca-O and Ba-O distributions. A consideration of the bonding shows that the oxygen atoms in the SO4 2- groups do not participate in the silicate network, and as such constitute a third type of oxygen, ‘non-network oxygen’, in addition to the bridging and non-bridging oxygens that are bonded to silicon atoms. Thus each individual sulphate group is surrounded by a shell of modifier, and is not connected directly to the silicate network. The addition of SO3 to the glass leads to a conversion of oxygen atoms within the silicate network from non-bridging to bridging, so that there is a repolymerisation of the silicate network. There is evidence that SO3 doping leads to changes in the form of the distribution of Na-O bond lengths, with a reduction in the fitted short bond coordination number, and an increase in the fitted long bond coordination number, and this is consistent with a repolymerisation of the silicate network. In contrast, there is no evidence that SO3 doping leads to a change in the distribution of Li-O bond lengths, with a total Li-O coordination number consistently in excess of four.
Item Type: | Article |
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Uncontrolled Keywords: | Physical Chemistry; 09 Engineering; 03 Chemical Sciences; 10 Technology |
Identification Number: | https://doi.org/10.1021/acs.jpcc.9b10924 |
Page Range: | 5409-5424 |
SWORD Depositor: | Symplectic Elements |
Depositing User: | Symplectic Elements |
Date Deposited: | 10 Feb 2020 14:19 |
Last Modified: | 18 Mar 2021 02:33 |
URI: | https://shura.shu.ac.uk/id/eprint/25807 |
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