X-ray diffraction and29Si NMR were used to monitor structural changes in lithium silicate gels following heat treatments at temperatures from 200 to 850 °C. The gels were prepared in two ways: polymerized gels were prepared by hydrolysis of tetraethylorthosilicate (TEOS) with a methanol-water-LiNO3 or LiOH solution and infiltrated gels were prepared by soaking colloidal silica gels in methanolic LiOH or aqueous LiNO3 solution. All of the gels have approximately 15 mol% Li2O. X-ray diffraction analysis indicated that the polymerized gel with LiNO3 as a precursor had the highest crystallization temperature (∼ 800 °C), while the infiltrated gel with LiOH as a precursor had the lowest crystallization temperature (∼ 200 °C). It was also found that Li2SiO3 formed preferentially at lower temperatures while Li2Si2O5 crystallized at higher temperatures. The change of local structure in heat treated samples was probed by29Si NMR. The sequence of formation of various non-bridging silicate and silanol groups is consistent with the results from X-ray diffraction.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry