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Lithium-sodium metaborate glasses: structural aspects and vitrification chemistry

1994; Elsevier BV; Volume: 167; Issue: 1-2 Linguagem: Inglês

10.1016/0022-3093(94)90372-7

1873-4812

Georgios D. Chryssikos, J.A. Kapoutsis, E. I. Kamitsos, A.J. Patsis, Amanda J. Pappin,

Luminescence Properties of Advanced Materials

Vibrational and devitrification techniques are employed to investigate the structure and glass-forming ability of xNaBO2 · (1 − x)LiBO2 glasses with 0 ⩽x⩽ 0.75. Alkali substitution is found to result in non-additive network changes due to the appearance of structures encountered in the newly discovered compound Li3NaB4O8 (x = 0.25). A decrease of Tg with x is observed and attributed mainly to the partial suppression of the formation of tetrahedra-containing, β′- and γ-LiBO2-type, arrangements in the glass network. The dependence of the crystallization products on temperature is very pronounced for x = 0 and progressively diminishes for x → 0.25. This diminishment is taken to indicate that, upon increasing x (0 ⩽x⩽ 0.25), the structural rearrangements associated with the liquid-to-glass transition become less pronounced. In turn, alkali mixing in the system under investigation is correlated with decreasing melt 'fragility' and a less pronounced pathway glass morphology. Such remarks may be important in assessing the mixed alkali effect from a structural viewpoint, especially since they are compatible with earlier findings on lower modification borate analogs.