Structural design of sealing glasses

Requirements for enhanced component performance and reliability have led to the development of novel glass compositions for a variety of hermetic sealing applications. The development of technologically useful glss compositions was based on an understanding of the relationships between the molecular-level glass structure and important physical properties. The properties of the alkaline earth aluminoborate glasses for lithium batteries are sensitive to changes in B-and Al-coordination number, characterized by solid state nuclear magnetic resonance (NMR) spectroscopy. In general, the most useful compositions have structures that are dominated by tetrahedral Band Al-sites. Mixed alkali aluminophosphate glasses were developed for aluminum electrical connectors. The properties of sodium aluminophosphate glasses depend on the O/P ratio and significant property changes (e.g. maxima in T-g and refractive index) occur when O/P exceeds the pyrophosphate limit at 3.5. Associated with these property changes is a decrease in the average Al-coordination number, from six to four, at O/P > 3.5. Raman spectroscopy provides additional information about the aluminophosphate network. Finally, zinc borophosphate glasses are developed for seals in flat panel displays. Boron-11 NMR shows that tetrahedral barons are preferred in xB(2)O(3)(1-x)(PO3)(2) and in yB(2)O(3)(1-y)Zn2P2O7 glasses for x < 0.4 and y < 0.2. Raman spectroscopy reveals the concomitant evolution from a phosphate to a borophosphate network with increasing x and y. (C) 1997 Elsevier Science B.V.