The effect of heat treatment time on lithium-containing Al2O3‒SiO2 gels: a study by 7Li NMR

S. Szu, A. M. Buckley, Martha Greenblatt, Lisa Klein

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Abstract

Samples with nominal composition 15(LiCl)2-7.7Al2O3-77.3SiO2 were prepared by the sol-gel method and heat treated at 500°C for 5, 10, 20 and 100 h. Both powder X-ray diffraction and transmission electron microscopy data confirm that the heat-treated gels are amorphous. The transmission electron microscopy data and the temperature dependence data of the spin-lattice relaxation time, T1, of the 7Li nucleus by NMR, do not differ within experimental error for gels heat-treated for different times. Two types of relaxation processes are observed in the gels. A fast relaxation of T1f = 1.5 ± 0.08 is attributed to network-associated lithium ions, in which the lithium ions are either associated with non-bridging oxygens on the silica tetrahedra or with four-coordinated aluminum for charge compenation. A slow relaxation process T1s = 0.20 ± 0.01 is ascribed to lithium in nano-scale particulate LiCl in the pores of the gel. The T1 data indicate that the difference between these two relaxation processes is averaged as the temperature increases.

Original languageEnglish (US)
Pages (from-to)129-136
Number of pages8
JournalJournal of Non-Crystalline Solids
Volume146
Issue numberC
DOIs
Publication statusPublished - 1992

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All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Materials Chemistry

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