Structural manifestations of the mixed-alkali effect: NMR studies of sodium rubidium borate glasses

The spatial distribution of the sodium ions in sodium rubidium borate glasses with composition [(Na2O)x(Rb2O)1−x]y(B2O3)1−y (0⩽x⩽1, y=0.2 and 0.3) has been studied by complementary high resolution and dipolar solid state NMR experiments. 11B{23Na} rotational echo double resonance (REDOR) measurement...

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Bibliographic Details
Published in:Journal of non-crystalline solids 2005-11, Vol.351 (43-45), p.3521-3529
Main Authors: Epping, Jan Dirk, Eckert, Hellmut, Imre, Árpád W., Mehrer, Helmut
Format: Article
Language:English
Subjects:
Condensed matter: structure, mechanical and thermal properties
Disordered solids
Exact sciences and technology
Glasses
Physics
Structure of solids and liquids
crystallography
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Summary:The spatial distribution of the sodium ions in sodium rubidium borate glasses with composition [(Na2O)x(Rb2O)1−x]y(B2O3)1−y (0⩽x⩽1, y=0.2 and 0.3) has been studied by complementary high resolution and dipolar solid state NMR experiments. 11B{23Na} rotational echo double resonance (REDOR) measurements indicate that the trigonal BO3/2 groups and the four-coordinate BO4/2- units experience 23Na local dipolar fields of similar magnitudes, consistent with a random distribution of the overall cation population. Combined with this result, 23Na–23Na homonuclear second moments measured via 23Na spin echo decay spectroscopy reveal non-statistical mixing of sodium and rubidium ions in relation to each other, suggesting some preference of like-cation interactions. These results support the idea that the details of unlike-cation mixing are influenced by the size differences between the ions involved.
ISSN:0022-3093
1873-4812
DOI:10.1016/j.jnoncrysol.2005.08.034