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In the aforementioned depolymerization reaction, an NBO is conventionally depicted with a negative charge to balance the positive charge on the Na⁺ modifier cation, shown to indicate ionic bonding between the anions and cations. Although this reaction only shows two NBOs adjacent to the Na⁺, the coordination numbers of modifier cations are actually larger, typically greater than four. It is thus inevitable that the modifier cations are clustered in some way. According to Greaves' modified random network (MRN) model (Chapter 2.5), the modifiers coalesce into channels if their content exceeds a percolation limit. There are thus two interlacing sublattices: the network regions constructed from network formers and the inter‐network regions made up of modifiers (see Figure 8a in Chapter 2.5). Such a microstructure has important consequences for the physical and transport properties (e.g. ionic conductivity).

Table 1 Structural classification of commonly studied oxides in glasses. Frequently found M─O coordination numbers (where M indicates the cation) are given in brackets.