Effect of additives on the distribution of phosphorus associated with phase separation of borosilicate glasses

Abstract

Sodium borosilicate glasses containing phosphorus were prepared, and the effect of Al₂O₃ and TiO₂ addition on the distribution behavior of phosphorus atoms associated with the phase separation was investigated. After heat treatment, a phase separation by the spinodal decomposition was commonly confirmed by SEM observation. In the additive-free sample, phosphorus was preferentially distributed into B₂O₃-rich phase after the phase separation, and after adding Al₂O₃ or TiO₂, the amount of phosphorus distributed into SiO₂-rich phase increased. It was also suggested that TiO₂ had a stronger influence on the phosphorus distribution into SiO₂-rich phase than Al₂O₃. ³¹P MAS-NMR revealed that most of phosphorus atoms in the additive-free glass were present in PO₄ units consisting of two terminal oxide ions, and the terminal oxide ions decreased and increased after the additions of Al₂O₃ and TiO₂, respectively. It was suggested that this structural change brought about a change in the distribution of phosphorus.