Bulk and interfacial ionic conduction in LiI/Al2O3 mixtures

We have studied physical mixtures of LiI and nanoscale particles of Al2O3, prepared in pellet form under pressure, by X-ray diffraction, complex impedance, and wide-line Li-7 and I-127 and high resolution Li-7 NMR spectroscopy. Enhancement in ionic conductivity by the addition of Al2O3, is observed, although there is also an increase in grain boundary resistance. The high resolution (MAS) NMR method clearly resolves two or more distinct Li+ sites, one characteristic of bulk LiI and the rest associated with surface/interface regions. The site populations depend strongly on mix composition and temperature, and are correlated with the ionic conductivity behavior. (C) 1998 Published by Elsevier Science BN. All rights reserved.