What is it about?
We investigated the structural changes that occur in oxide glasses and melts under high pressure conditions. The chapter is a contribution to the book entitles "Magmas under Pressure: Advances in High-Pressure Experiments on Structure and Properties of Melts."
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Why is it important?
We consider the structural response of oxide glasses and melts to high-pressure conditions, and focus on the transformations that take place to the tetrahedral AO4 or planar triangular AO3 network-forming motifs (A = Si, Ge, or B) of the ambient pressure materials. The oxygen-packing fraction eta_O plays a key role in determining when these structural changes are likely to occur. Densification occurs in stages where a plateaux of stability for a given type of network-forming motif is followed by a regime of change. The conversion of tetrahedral AO4 to octahedral AO6 motifs starts at eta_O = 0.58, and fivefold coordinated AO5 units act as important intermediaries during this transformation. The position of the first-sharp diffraction peak in measured diffraction patterns is sensitive to eta_O, enabling it to be used as a marker for structural change. The transformation of AO6 to higher coordinated structural motifs starts when eta = 0.72.
Perspectives
It is informative to explore the structural changes that occur to amorphous oxides under high-pressure conditions and related them to features in the measured diffraction patterns.
Professor Philip S Salmon
University of Bath
Read the Original
This page is a summary of: Densification Mechanisms of Oxide Glasses and Melts, January 2018, Elsevier,
DOI: 10.1016/b978-0-12-811301-1.00013-7.
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