Abstract
High-quartz and keatite are two of the high-temperature silica phases. Both have negative thermal expansion and both can be stabilized by partial replacement of Si with Al and Li. Some current data are used in this paper to extend and refine the stabilization principle first outlined by Buerger. Based upon this study, it is the interstitial cations like Li that stabilize the high-temperature structure by effectively reducing the excess void space. Thus the high-temperature structure is buttressed and preserved by preventing it from collapsing into the low-temperature form at the transformation temperature. It is also found that Li can best stabilize the high-quartz and the keatite phases because of its unique characteristics. First, Li has the precise size to fit into the interstitial space with ease. Second, Li has the ideal combination of valence and coordination number so that it can best balance the local charge. Some structural data are presented to support these observations.
