INFLUENCE OF SMALL ADDITIONS OF LI2O RAW-MATERIALS ON GLASS MELTING

For a container glass composition up to 1 mol% of the alkali oxide was substituted by Li2O in steps of approximate to 0.2 %. The lithia was added as Li2CO3 and as spodumene, respectively. As shown earlier [I] L i2O reduces the viscosity of the melts considerably, irrespective of t he Li2O source. However, melt formation, carbonate decomposition, sili cate and silicate melt formation processes during raw materials reacti ons are considerably accelerated by Li2CO3 addition only, whereas Li2O in the spodumene silicate does not enhance these reactions. The finin g of the melt and the corrosion behavior of refractories are strongly influenced also by the lower viscosity melts. Thus, the corrosion rate may be diminished by temperature reduction at constant viscosity. For technical purposes the glasses are very stable against crystallizatio n, however, thermal analysis shows that the higher the Li2O content is , the faster the crystal growth proceeds. The surface tension of the g lass melts decreases and the water leach resistance of the solid glass es is enhanced with increasing Li2O content. The Li+ ions are less pol arizable and, due to their high Dietzel field strength, the glass stru cture is tightened compared with that of Li2O-free glass. In conclusio n, the substitution of small amounts of Li2O instead of Na2O and/or K2 O shows several advantages. At low temperatures different raw material s reactions are accelerated and at high temperature the decrease in me lt viscosity is decisive.