Infrared and MAS NMR Spectroscopic Studies of Al18B4O33

The IR spectrum and 11B and 27Al MAS NMR spectra of Al18B4O33 are presented and discussed in relation to the possible existence of boron atoms substituting for aluminum atoms. TheIR spectrum shows that the strong vibrations of the BO3 groups are present in the 1 500～1 200em-1 region, and very weak bands of BO4 units are present in the region from 1 000 to 1 100cm-1. 11B MAS NMR spectrum indicates that the strong signal for BO3 units appears in the region from δ +5 to δ +20, and the very weak signal for BO4 units is at about δ-1, while 27AlMAS NMR spectrum shows five peaks at about δ +62, +42. 1, +14,-4.7 and-6.4, originating from AlO4, AlO4, A1O5, AlO6 and AlO6, respectively. These results reveal that there areminor BO4 units in Al18B4O33, indicating that a small amount of B atoms substitute for Al atomsin the 4-fold coordination.