THE NONISOTHERMAL DEVITRIFICATION OF LITHIUM GERMANATE GLASSES

The non-isothermal devitrification of lithium germanate glasses, exami ned by DTA and XRD, is reported and discussed. The glass compositions are expressed by the general formula: xLi2O(1-x)GeO2 with x = 0.050, 0 .125, 0.167, 0.200 and 0.250. All the glasses studied, unlike GeO2 gla ss, exhibit internal crystal nucleation without the addition of any nu cleating agent. The devitrification processes occur in one or more ste ps. Phases which crystallized at each step are identified and crystall ization mechanisms proposed. These crystallization mechanisms are rela ted to structures of the crystallizing phases. Activation energy value s as well as those for glass transition temperatures, do not vary line arly with increase in Li2O content but pass through a maximum at x = 0 .200.