Differential Thermal Analysis of Glass Mixtures Containing SiO2, GeO2,  B 2O3, and  P 2O5

Abstract

The glassy phases of Formula , Formula , Formula , and Formula as well as selected pseudo‐binary, pseudo‐ternary, and pseudo‐quaternary compositions of these compounds have been examined for glass transitions by differential thermal analysis (DTA) in the context of reflow of doped germanosilicate glasses. Formula does not exhibit a glass transition to temperatures above 1135°C. Formula appears to exhibit a glass transition around 578°C, while Formula appears to exhibit a glass transition in the range of 257-268°C. Although the glass transition temperature of Formula could not be determined, the transition and melting behavior of the H, O, and O′ phases have been reevaluated. Moreover, a new mechanism for conversion from H phase to O phase is presented. Namely, the melting of H phase followed by the spontaneous recrystallization of the resulting liquid to form the O phase was observed by DTA. Germanosilicate mixtures exhibited no glass transition, but the germanoborates' glass transition temperatures increased linearly with increasing Formula content. Examination of germanoborosilicates indicated that the addition of any germanosilicate composition to Formula causes a linear increase in glass transition temperature with total germanosilicate mole fraction, independent of the Formula mole ratio. Pseudo‐binary combinations of Formula showed no thermal anomalies on heating or cooling cycles following an initial thermal cycle. However, pseudo‐binary combinations of Formula exhibited exotherms on cooling following initial heating cycles, which may indicate the occurrence of crystallizations that might interfere with reflow phenomena. Pseudo‐quaternary combinations exhibited no thermal anomalies on heating or cooling. © 1999 The Electrochemical Society. All rights reserved.