Structural Role of Fluoride in the Ion-Conducting Glass System B₂O₃−PbO−LiF Studied by Single- and Double-Resonance NMR

Abstract

The local structure of an ion-conducting glass with nominal composition 50B2O3−10PbO−40LiF has been investigated by complementary 7Li, 11B, 19F, and 207Pb single- and double-resonance experiments. The results give insight into the structural role of the lithium fluoride additive in borate glasses: (1) LiF is seen to actively participate in the network transformation process contributing to the conversion of three- into four-coordinate boron units, as shown by 11B single-resonance as well as by 11B{19F} and 19F{11B} double-resonance experiments. (2) 19F signal quantification experiments suggest substantial fluoride loss, presumably caused by formation of volatile BF3. A part of the fluoride remains in the dopant role, possibly in the form of small LiF-like cluster domains, which serve as a mobile ion supply. (3) The extent of lithium−fluorine and lead−fluorine interactions has been characterized by 7Li{19F} and 207Pb{19F} REDOR and SEDOR experiments. On the basis of these results, a quantitative structural description of this system has been developed.

Structural Studies of Fluoroborate Laser Glasses by Solid State NMR and EPR Spectroscopies

“…While such gross mass losses are not observed for the BPF x glasses, the fluorine content of these glasses is also clearly reduced to about 40–80% of the original quantity batched. As previously discussed, , this fluoride loss most likely occurs through F/O exchange via the melting atmosphere. Obviously, these losses must be taken into consideration when discussing the experimental NMR results.…”

“…Therefore, they are considered to be a good choice as hosts for RE ions and, in fact, have turned out to be one of the most promising optical materials. − In addition, glasses containing heavy metal oxides such as PbO, CdO and Bi 2 O 3 , and lead borate, and fluoroborate glasses, in particular, have been studied in much detail because of their low phonon energies, high refractive indexes, low glass transition temperatures, high polarizabilities, and good dispersal of RE ions. − Other PbF 2 containing RE doped glass compositions have also shown promise for the preparation of RE doped glass ceramics, − with the perspective that the rare-earth ions are dispersed within the lattice of a PbF 2 nanophase . In addition, lead fluoroborate glasses show fast anion conducting properties, making them an interesting material for electrochemical devices. − Despite this considerable interest, a fundamental understanding of these properties on the basis of the structural organization of these glasses is still missing. Solid state nuclear magnetic resonance (NMR) spectroscopy has proven to be a powerful tool in addressing such structural issues, especially for disordered materials, due to its well-proven ability to provide local structural information. , Likewise, electron paramagnetic resonance of RE dopant ions is receiving increasing attention as a complementary structural probe, providing particular information on the local environment of the fluorescent dopant species. − …”

Structure-property relations in new fluorophosphate glasses singly- and co-doped with Er3+ and Yb3+

“…As fluoride losses and/or replacement by oxide species are an important issue in the preparation of oxyfluoride glasses, the total F content was quantified via NMR using a previously described standard addition method on samples containing a weighed amount of sodium fluoride, NaF [37]. These spectra were obtained as rotor synchronized Hahn spin echoes on samples spinning at 25.0 kHz.…”

Short and Medium Range Order in Ion-Conducting Glasses Studied by Modern Solid State NMR Techniques

“…Unfortunately, in oxysulfide, oxynitride and in most oxyhalide glasses such ex- periments have been hampered by the lack of suitable NMR active isotopes. Recently, however, the proof of concept was given for a glass of composition 48B 2 O 3 -10PbO-28LiF-6Li 2 O [97]. As shown in Fig.…”