Structural investigation of borosilicate glasses by using XAFS measurement in soft X-ray region (2) (Joint research)

The local structure of glass-forming elements and waste elements in borosilicate glasses varies with its chemical composition. In this study, borosilicate glass frit and simulated waste glass samples were prepared and the chemical state regarding boron(B), silicon(Si) and waste elements of iron(Fe), cesium(Cs) were estimated by using XAFS measurement in soft X-ray region. Following results were obtained by XAFS measurements of simulated waste glass surfaces after immersion test to investigate the long chemical stability. (1) As the leaching time of glass samples in immersion test passed, the Cs M₅, M₄-edge XANES spectra disappeared and the Fe L₃, L₂-edge spectra changed. (2) A new compound was formed on the sample surface after the immersion test, and these changes in the surface state were confirmed by Raman spectroscopy. However, it became difficult to obtain a clear B K-edge XANES spectrum by forming a compound on glass surfaces. The Si K-edge XANES spectra of borosilicate glass frits with different Na₂O content were measured, and following was confirmed. (1) As the Na₂O concentration increases in borosilicate glass frit, the K-edge peak of Si shifts to the low energy side. (2) The intensity of the Si K-edge peak is maximum when the Na₂O content in glass frits was about 7wt%. (author)