Phase separation of borosilicate glass containing phosphorus

Sodium borosilicate glasses containing P₂O₅ and Al₂O₃ were prepared, and the behavior of phosphorus associated with the phase separation and the effect of Al₂O ₃ addition have been investigated. After the heat treatment, phase separation by spinodal decomposition was observed in the all samples. In the Al₂O₃-free glasses, phosphorus was preferentially distributed into B₂O₃-rich glass phase after the phase separation. With increasing Al₂O₃ content, the amount of phosphorus distributed into SiO₂-rich glass phase increased. According to ³¹P MAS NMR measurements, in the Al₂O ₃-containing glasses, Q⁴ units free from terminal oxygen atoms were formed. It was suggested that the distribution of phosphorus depend on the PO₄ units.