Wavenumber (cm−1) | FT-IR assignment |
| Stretching vibrations of Bi-O bonds in strongly distorted BiO6 octahedral units, B-O-B bond bending vibrations. |
| Symmetric stretching vibrations of Bi-O bonds in pyramidal BiO3 units, O3B-O-BO3 bending vibrations. |
| Symmetric stretching vibrations of Bi-O bonds in pyramidal BiO3 units, stretching vibrations of B-O bonds in BO4 units from diborate groups. |
990 - 1080 cm−1 | Stretching vibrations of B-Q bonds in BQ4 units from tri-, tetra-, and penta-borate groups. |
| Stretching vibrations of B-O bonds in BO3 units from meta- and ortho-borate groups. |
1300 - 1500 cm−1 | Asymmetric stretching vibrations of B-O bonds in BO3 and BQ2O− units. |