Structural Studies of Rare Earth-Doped Fluoroborosilicate Glasses by Advanced Solid-State NMR

The detailed local structures of fluoroborosilicate glasses with the compositions of (50 + x )SiO 2 –(20 – x )B 2 O 3 –10Na 2 O–10NaF–10YF 3 ( x = 0, 5, 10, 15 mol %) were investigated by advanced one- and two-dimensional solid-state nuclear magnetic resonance (SSNMR) techniques. The borosilicate glass network is characterized by 29 Si and 11 B magic angle spinning NMR (MAS NMR) spectra. 29 Si MAS spectra show that the silicate network strengthens with the decrease of the B 2 O 3 content. Two three-coordination boron species (B (3) -ring, B (3) -nonring) and two four-coordination boron species (BO 4, BO 3 F) are observed in the 11 B MAS spectra. The two types of B (4) species are identified by 11 B triple-quantum magic angle spinning (TQMAS) and J -coupling-based 11 B{ 19 F} heteronuclear multiple quantum coherence ( J -HMQC) methods. The F – species are confirmed by 19 F MAS spectra and a 19 F{ 23 Na} rotational echo double resonance (REDOR) method, revealing the existence of Na–F–B and multiple Na–F–Y linkages. The clustering of F – ions is proved by 19 F static spin echo results, which indicate that B 3+ ions have a dispersive effect on F – ions. 11 B/ 23 Na REDOR results show that the distribution of Na + around B (3) and B (4) is similar, and independent of the content of B 2 O 3 . On the basis of these results, a quantitative atomic structure evolution with glass compositions is investigated.