The title phases are prepared by the sol-gel route employing prehydrolyzed tetraethylorthosilicate (TEOS) and Al, Li or Mg nitrates in aqueous solution. Amorphous xerogels are obtained at 400-degrees-C; they are characterized as high to very high surface oxides with peculiar pore-size distributions. High-quartz solid-solution phases originate from these xerogels by heating at 600-degrees-C (lithia-containing compositions) or at 900-degrees-C (magnesia-containing composition). They are characterized by X-ray powder diffraction and FTIR spectroscopy as phases with strong disorder in the cation distribution, both in the AlSi sites and Li sites, with the exception of the stoichiometry LiAlSiO4, which shows a certain degree of Li and Si/Al ordering.
High-quartz Solid-solution Phases From Xerogels With Composition 2MgO.2Al2O3.5SiO2 (mu-cordierite) and Li2O.Al2O3.nSiO2(n=2 To 4)(beta-eucryptite) - Characterization By Xrd, Ftir and Surface Measurements
BUSCA, GUIDO;
1993-01-01
Abstract
The title phases are prepared by the sol-gel route employing prehydrolyzed tetraethylorthosilicate (TEOS) and Al, Li or Mg nitrates in aqueous solution. Amorphous xerogels are obtained at 400-degrees-C; they are characterized as high to very high surface oxides with peculiar pore-size distributions. High-quartz solid-solution phases originate from these xerogels by heating at 600-degrees-C (lithia-containing compositions) or at 900-degrees-C (magnesia-containing composition). They are characterized by X-ray powder diffraction and FTIR spectroscopy as phases with strong disorder in the cation distribution, both in the AlSi sites and Li sites, with the exception of the stoichiometry LiAlSiO4, which shows a certain degree of Li and Si/Al ordering.
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