Polyhedral Arrangements in Lanthanum Aluminoborate Glasses

We have used magic‐angle spinning nuclear magnetic resonance (MAS NMR) and Raman spectroscopy to examine the polyhedral arrangements in ternary lanthanum aluminoborate glasses. We have characterized two glass‐forming series: x Al 2 O 3 ·(1− x )LaB 3 O 6 and 0.25La 2 O 3 · y Al 2 O 3 (1− y )‐B 2 O 3 . 11 B MAS NMR reveals a decrease in the fraction of four‐coordinated boron atoms with increases in the Al 2 O 3 content in both series. 27 Al MAS NMR has detected four‐, five‐ and six‐coordinated aluminum atoms in complex aluminoborate networks similar to those reported elsewhere for alkaline‐earth aluminoborate glasses. Raman spectroscopy reveals a variety of borate and aluminoborate moieties, including isolated groups as well as methaborate chains and rings. These results indicate that the La 3+ ion acts as a modifier to the aluminoborate network.