CRYSTALLIZATION OF LITHIUM DISILICATE AND METASILICATE SOLID-SOLUTIONS FROM LI2O-SIO2 GLASSES

The devitrification behaviour of fourteen glasses in the Li2SiO3-Li2Si 2O5 system has been studied by x-ray diffraction and microscopy techni ques. Crystallisation products are metastable lithium di- and metasili cate solid solutions (LS2-ss, LS-ss). Unit cell constants indicated th at the LS2-ss composition ranges to approximate to 39 mol% Li2O for te mperatures below 550 degrees C. For LS-ss a lithia deficient limit les s than or equal to 40 mol% has been detected at 700 degrees C. The nat ure of primary solid solution in a 40Li(2)O.60SiO(2) glass is a functi on of the melting history as well as of the annealing conditions. Sphe rulitic crystallites were observed in this glass containing intergrowi ng sections of LS2-ss and LS-ss.