EFFECT OF GALLIUM OXIDE ON CRYSTALLIZATION AND THERMAL-EXPANSION BEHAVIOR OF LOW-K GLASS COMPOSITE

Cristobalite is formed when borosilicate glass (Corning Code 7740) is sintered at temperatures ranging from 700 degrees C to 1000 degrees C. With added gallium oxide content greater than a critical value, the c ristobalite formation in the borosilicate glass is completely prevente d at the sintering temperatures investigated, and the critical gallium oxide content increases with decreasing sintering temperature. The ab ove result, similar to that observed in Al2O3/borosilicate glass syste m, is attributed to a strong coupling between Ga+3 from Ga2O3 and Nafrom borosilicate glass. The observed coupling reaction causes segrega tion of Na+ in borosilicate glass to gallium oxide, thus forming a Na and Ga+3-rich reaction layer around gallium oxide particles at a rate which prevents formation of cristobalite.