TY - JOUR
T1 - The local environment of trivalent lanthanide ions in sodium silicate glasses
T2 - A neutron diffraction study using isotopic substitution
AU - Wilding, Martin
AU - Badyal, Yaspal
AU - Navrotsky, Alexandra
N1 - Funding Information:
This work has benefited from the use of the Intense Pulsed Neutron Source at Argonne National Laboratory. This facility is funded by the US Department of Energy, BES-Materials Science, under Contract W-31-109-Eng-38.
PY - 2007/12/15
Y1 - 2007/12/15
N2 - Neutron diffraction data on lanthanide-bearing sodium silicate glasses were collected using the glass, liquid and amorphous materials diffractometer (GLAD) at the intense pulsed neutron source (IPNS), Argonne. Measurements were made on four glass samples; a sodium silicate base glass with no added lanthanide, a sample with 6 mol% La2O3 added to the base composition, and two isotopically-distinct samples containing 6 mol% Dy2O3. Of the Dy-bearing samples, one contained natural enrichment Dy, and the other a 'null scattering' mixture of natural and 162Dy isotopes. The first-order isotope difference of the scattering from the Dy-bearing samples revealed a Dy-O nearest-neighbor distance of 2.3 Å and a mean coordination number of 5.9 oxygen atoms around each dysprosium ion; the latter is in good agreement with the coordination number derived from bond-valence theory. The results for the La-bearing glass were also consistent with a sixfold coordination of oxygen atoms around the rare earth. The diffraction data are used in combination with Reverse Monte Carlo modeling techniques to interpreter the structural role of the rare earth ions. From these models, it is apparent that there is competition between monovalent sodium ions and the rare earth ions for the same non-bridging oxygen atoms. As a result the addition of rare earth ions appears to cause disruption of the Na-rich percolation domains characteristic of the sodium silicate base glass. These neutron results are consistent with the formation of a specific lanthanide Q3 as suggested by NMR and Raman spectroscopy, but offer no direct evidence for the formation of 'oxide-like' lanthanide clusters.
AB - Neutron diffraction data on lanthanide-bearing sodium silicate glasses were collected using the glass, liquid and amorphous materials diffractometer (GLAD) at the intense pulsed neutron source (IPNS), Argonne. Measurements were made on four glass samples; a sodium silicate base glass with no added lanthanide, a sample with 6 mol% La2O3 added to the base composition, and two isotopically-distinct samples containing 6 mol% Dy2O3. Of the Dy-bearing samples, one contained natural enrichment Dy, and the other a 'null scattering' mixture of natural and 162Dy isotopes. The first-order isotope difference of the scattering from the Dy-bearing samples revealed a Dy-O nearest-neighbor distance of 2.3 Å and a mean coordination number of 5.9 oxygen atoms around each dysprosium ion; the latter is in good agreement with the coordination number derived from bond-valence theory. The results for the La-bearing glass were also consistent with a sixfold coordination of oxygen atoms around the rare earth. The diffraction data are used in combination with Reverse Monte Carlo modeling techniques to interpreter the structural role of the rare earth ions. From these models, it is apparent that there is competition between monovalent sodium ions and the rare earth ions for the same non-bridging oxygen atoms. As a result the addition of rare earth ions appears to cause disruption of the Na-rich percolation domains characteristic of the sodium silicate base glass. These neutron results are consistent with the formation of a specific lanthanide Q3 as suggested by NMR and Raman spectroscopy, but offer no direct evidence for the formation of 'oxide-like' lanthanide clusters.
KW - Medium-range order
KW - Monte Carlo simulations
KW - Neutron diffraction/scattering
KW - Rare-earths in glasses
KW - Short-range order
KW - Silicates
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U2 - 10.1016/j.jnoncrysol.2007.06.071
DO - 10.1016/j.jnoncrysol.2007.06.071
M3 - Article
AN - SCOPUS:36549049886
SN - 0022-3093
VL - 353
SP - 4792
EP - 4800
JO - Journal of Non-Crystalline Solids
JF - Journal of Non-Crystalline Solids
IS - 52-54
ER -