Crystallization of lithium aluminosilicate gels

In lithium aluminosilicate gels, the crystalline phases and the temperatures at which they appear depend on the preparation method used. Samples were prepared by adding anhydrous tetraethyl orthosilicate (TEOS) to a solution of methanol, water and the nitrates of lithium and aluminium. The amount of methanol in the solution was varied to create miscible and immiscible compositions. With high levels of methanol, the solutions appeared homogeneous throughout gelling. With little methanol, the solutions initially were cloudy but cleared before gelling. Samples were dried thoroughly before gel textures were probed with gas sorptions techniques. When dried gels were heated, they crystallized. In low alcohol gels, lithium disilicate and quartz appeared at around 700°C. In high alcohol gels quartz appeared only at around 650°C. The higher crystallization temperatures were found in finer textured gels. It appears that the low alcohol gel with its finer texture does not crystallize as readily as high alcohol gels because the lithium is distributed more uniformly.