Some structural features of alkali aluminofluorophosphate glasses

Glasses of compositions (mol %) 50NaPO(3) . 20AlF(3) . 30LiF and 50NaPO(3) . 25AlF(3) . 25LiF are synthesized. It is elucidated how the AlF3 content affects the glass properties (density rho, refractive index n(e), linear thermal expansion coefficient a, and glass transition temperature Tg) and IR spectra. Analysis of the glass properties and IR spectra at different compositions demonstrates that the structure of the studied glasses is based on the [PO4](3-), [P2O7](4-), [PO3F](2-), and [AlF6](3-) groupings. The substitution of AlF3 for LiF results in a more closely packed arrangement of structural elements and an increase in the number of pyrophosphate, [AlF6](3-), and [PO3F](2-) groupings. It is revealed that the IR spectra of the studied glasses are similar in character.