Conductance and spectroscopy of protonic beta and beta″-aluminas |
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Authors: | G.C. Farrington J.L. Briant H.S. Story W.C. Bailey |
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Affiliation: | General Electric Corporate Research and Development, P.O. Box 8, Schenectady, NY 12301, U.S.A.;State University of New York at Albany, Albany, NY 12222 U.S.A. |
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Abstract: | Five protonic beta and beta″-aluminas; viz hydrated sodium beta-alumina (1,24Na2O·11Al2O3), hydronium beta-alumina (1.24H2O·11Al2O3·2.6H2O), partially dehydrated hydronium beta-alumina (1.24H2O·11Al2O3·1.3H2O), hydrogen beta-alumina (1.24H2O·11Al2O3) and hydronium beta″-alumina (0.84H2O·0.8MgO·5Al2O3·2.8H2O) were examined by broad band nuclear magnetic resonance from ?196°C to 200°C. The spectra of hydronium beta-alumina and hydronium beta″-alumina are consistent with a mixed composition of H2O, H3O+ and H+ species in the conducting plane. Hydrogen beta-alumina and partially dehydrated hydronium beta-alumina appear to contain only relatively isolated (2.6–2.7Å) protons; no evidence of molecular water or hydronium ions is found. Water molecules intercalated into the conduction plane of sodium beta-alumina do not appear to be in rapid motion, even at 167°C, but are relatively stationary. The onset of motional narrowing in hydronium beta″-alumina occurs at ?40°C but not until +30°C in hydronium beta-alumina. This is consistent with the higher conductivity reported for hydronium beta″-alumina, 10?3–10?5 (ohm-cm)?1 at 25°C, in comparison to 10?10–10?11 (ohm-cm)?1 for hydronium beta-alumina at 25°C. |
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