Direct 17O NMR experimental evidence for Al–NBO bonds in Si-rich and highly polymerized aluminosilicate glasses

Abstract

By using solid-state ¹⁷O NMR spectroscopy, we provide the first direct experimental evidence for bonds between Al and non-bridging oxygen (NBO) ions in aluminosilicate glasses based on rare-earth (RE) elements, where RE = {Lu, Sc, Y}. The presence of ∼10% Al–NBO moieties out of all NBO species holds regardless of the precise glass composition, at odds with the conventional structural view that Al–NBO bonds are absent in highly polymerized and Si-rich aluminosilicate glass networks.