Sao Paulo State Univ UNESP, Inst Chem, BR-14800900 Araraquara, SP - Brazil
Total Affiliations: 3
Journal of Physical Chemistry C;
NOV 19 2020.
Web of Science Citations:
Bismuth-containing rare-earth codoped fluoride phosphate glasses are promising materials for superbroadband 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 P-31/F-19 double resonance NMR strategy, applied to glasses in the system (BiF3)(y)(50NaPO(3)-20Ba(PO3)(2)-20NaF-10BaF(2))(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. Na-23 MAS and Na-23[P-31] 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 M-2(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. (AU)