Composition dependence of element depth profiles in electron irradiated borosilicate glasses

The study of the electron irradiation effect on borosilicate glass is highly significant for the evaluation of its radiation resistance in a strong ionizing radiation environment. In this study, the element depth profiles of three types of ternary sodium borosilicate glasses (named NBS1, NBS2, and NBS3) induced by 1.2 MeV electron were characterized using time-of-flight secondary ion mass spectrometry (ToF-SIMS). The molar ratio R = [Na ₂O]/[B ₂O ₃] of NBS1, NBS2, and NBS3 were 1.34, 0.75, and 0.40, respectively, while the molar ratio K = [SiO ₂]/[B ₂O ₃] was fixed at 4.04. The results indicate that the amount by which the elements Na, B, and O decreased in the irradiated surface layer were different in all the samples. In particular, the depletion depths of all the elements were the same in the same irradiated NBS glass and increased with a decrease in the R value. The difference in the surface depletion of the three NBS glasses is related to the glass composition. In addition, the structure of the irradiated surface layer was characterized by X-ray photoelectron spectroscopy (XPS), the results of which suggested an increase in network polymerization and transformation of 4- to 3-coordinated boron. Combined with the structure of the irradiated surface layer, the formation mechanism of the irradiated surface layer was further discussed. These results are extremely important for understanding the changes in surface behavior caused by strong ionizing radiation.