Effect of water on the crystallization of Li2O-SiO2 glasses and gels

溶融法によって調整した微量(0.004～0.177 wt%)の水を含むLi2O-SiO2系ガラス粉末及び金属アルコキシド溶液の加水分解によって作ったリチウムケイ酸塩ゲル粉末の結晶化過程を示差熱分析,X線解析,赤外分光法によって研究した.その結果,水含有量が増すにつれて,ガラス転移温度及び核形成速度は低下し,結晶成長速度は増加することを見いだした.また,同一の酸化物組成でもガラスとゲルの結晶化過程は異なり,ガラスでは加熱の際に安定相のLi2Si2O5,ゲルでは準安定相のLi2SiOが析出することが分った.いったん溶融してガラスにすると,出発原料が炭酸塩又は酸化物結晶性粉末であるかゲルであるかに関係なく似た水含有量のガラスは似た結晶化挙動を示すことが確かめられた.The crystallization process of Li2O-SiO2 glass and lithium silicate gel powders has been investigated by means of differential thermal analysis, X-ray diffraction and infrared spectroscopy. The former was prepared by melting and contained 0.004～0.177 wt% water and the latter, by hydrolyzing metal alkoxide solutions. It is found that with increasing water content in the glass, the glass transition temperature and the rate of nucleation decrease, whereas the rate of crystal growth increases. It is also found that gels prepared from a metal alkoxide solution show a crystallization process different from glasses prepared by conventional melting method ; the crystalline phase precipitated from the former is metastable lithium metasilicate Li2SiO3 and that precipitated from the latter is stable lithium disilicate Li2Si2O3. It is also to be noted that the glass prepared by melting the gel shows a crystallization process similar to the glasses prepared by melting crystalline powders when their water contents are similar