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/spl deg/C to 1000/spl deg/C. With added gallium oxide content greater than a critical value, the cristobalite formation in the borosilicate glass is completely prevented at the sintering temperatures investigated, and the critical gallium oxide content increases with decreasing sintering temperature. The above result, similar to that observed in Al/sub 2/O/sub 3//borosilicate glass system, is attributed to a strong coupling between Ga/sup +3/ from Ga/sub 2/O/sub 3/ and Na/sup +/ from borosilicate glass. The observed coupling reaction causes segregation of Na/sup +/ in borosilicate glass to gallium oxide, thus forming a Na/sup +/ and Ga/sup +3/-rich reaction layer around gallium oxide particles at a rate which prevents formation of cristobalite.<
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