Effect of ³B Group in Rings on Special Dispersion of B₂O₃-SiO₂-ZrO₂-Ta₂O₅-Na₂O System Glass

Abstract

Borosilicate glasses, with xB₂O₃-(60-x)SiO₂-8ZrO₂-8Ta₂O₅-24Na₂O (7≤x≤59 mol%) composition, were fabricated by melt-quenching technique. NMR, UV-Vis, Raman and IR spectroscopic studies were utilized to investigate the structure of fabricated glasses. The NMR spectrum was deconvoluted into five Gaussian bands, assigned to ⁴B(0B,4Si), ⁴B(1B,3Si), ⁴B(2B,2Si), ³B(rings) and ³B(loose), to get their quantitative information. The relative dispersion deviation ΔP _g,F was attributed to the relative quantity of ³B (rings) but not all ³B groups, and B₂O₃ existed mainly as [BO₃] in rings firstly, and then as [BO₃] in loose condition. The UV-Vis spectra revealed that the quantity of non-bridging oxygen increased firstly and then decreased with increasing concentration of B₂O₃. Acting as complementary techniques, Raman and IR measurements revealed that four-coordinated boron and silica mainly existed as ⁴B-O-B, and Si-O-Si in Q², respectively, as chain structure but not framework structure, and [BØ₄] units prefered connections with borate rather than with silicate entities of the glass network in these studied glasses. In addition, the conclusion also certified that ³B in “loose” condition located in lower wavenumbers between 1 200^-1 600 cm-1 in Raman spectra.

Keywords

borosilicate glass / structure / NMR / Raman / relative dispersion deviation