Structure of alkali borosilicate glasses and melts according to Raman spectroscopy data

Using the technique of high-temperature Raman scattering spectroscopy, we studied the structure of glasses and melts of the systems Na₂O-B₂O₃-SiO₂, K₂O-B₂O₃-SiO₂, and Cs₂O-B₂O₃-SiO₂ with the relations ${{X_{M_2 O} } \mathord{\left/ {\vphantom {{X_{M_2 O} } X}} \right. \kern-0em} X}_{B_2 O_3 } = 1$ (M = Na, K, Cs) and ${{X_{SiO_2 } } \mathord{\left/ {\vphantom {{X_{SiO_2 } } X}} \right. \kern-0em} X}_{B_2 O_3 } = 3$ and 4/3. Based on the analysis of the registered spectra, we have shown that, at a high content of SiO₂, the disordered network of glasses is composed of the Q ⁴, Q ³, BO_4/2]^? tetrahedrons and BO_3/2 triangles. When the content of SiO₂ reduces, asymmetric borate triangles BØ_2/2O^? are formed in the structure in addition. A substantial part of borate tetrahedrons are included into the content of mixed borosilicate rings composed of two silicon-oxygen and two boron-oxygen tetrahedrons. The amount of borate structural units joined into purely borate superstructural groups increases with a decrease of the silicon oxide content, depends on the alkali kation type, and grows in the direction from Cs to Na. An increase in the temperature causes a decrease of various types of rings and growth of the concentration of asymmetric triangles. Both in glasses and melts, the fraction of the BO_2/2O^? triangles depends on the alkali cation type and increases in the succession Cs → K → Na. The results obtained present the basis to suggest that there is some differentiation in the mechanisms of structural reconstruction of the glasses under study by their heating depending on the modifying oxide.