BiF₃ Incorporation in Na/Ba Mixed Network Modifier Fluoride−Phosphate Glasses: Structural Studies by Solid-State NMR and Raman Spectroscopies

Bismuth-containing rare-earth co-doped fluoride phosphate glasses are promising materials for super-broadband near-infrared (NIR) emission with potential applications in optical amplification. To elucidate their structural organization this contribution develops a comprehensive multinuclear solid-state single and 31P/19F double resonance NMR strategy, applied to glasses in the system (BiF3)y(50NaPO3–20Ba(PO3)2–20NaF–10BaF2)100–y (y = 0, 5, 10, 20, 30, 40). To separately assess the influence of bismuth and fluorine constituents on the network structure, an additional set of (NaPO3)50–2x(Ba(PO3)2)20–x(NaF)20+2x(BaF2)10–x (x = 0, 2.5, 5.0, 7.5) glasses was also investigated. Introduction of alkali fluoride ions into phosphate glasses is shown to follow a new network modification scheme involving depolymerization of polyphosphate chains under the formation of F-bonded fluorophosphate units. However, a significant part of the fluoride stays separate, interacting exclusively with metal ion species. 23Na MAS and 23Na{31P} double resonance NMR results are consistent with a local sodium ion environment dominated by phosphate ions in the Bi-free system, whereas in the BiF3-containing glasses, the successive reduction of the dipolar second moment M2(Na-P) with increasing BiF3 content reflects the expected dilution effect, accompanied by increasing competition of the fluoride ions for ligation with the Na+ ions.

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Recommended citation: Gustavo Galleani, Henrik Bradtmüller, Hssen Fares, Silvia Helena Santagneli, Marcelo Nalin and Hellmut Eckert, “BiF$_3$ Incorporation in Na/Ba Mixed Network Modifier Fluoride-Phosphate Glasses: Structural Studies by Solid State NMR and Raman Spectroscopies”, Journal of Physical Chemistry C, 2020, 124, 25578−25587.