Structural studies on boroaluminosilicate glasses

Abstract Two series of boroaluminosilicate glasses having varying mole ratios of B 2 O 3 /Na 2 O (series 1) and B 2 O 3 /SiO 2 (series II) were prepared by conventional melt-quench method. Based on 29 Si and 11 B MAS NMR studies, it has been established that for series I glasses up to 15 mol% B 2 O 3 content, Na 2 O preferentially interacts with B 2 O 3 structural units resulting in the conversion of BO 3 to BO 4 structural units. Above 15 mol% B 2 O 3 for series I glasses and for all the investigated compositions of the series II glasses, silicon structural units are unaffected whereas boron exist in both trigonal and tetrahedral configurations. Variation of microhardness values of these glasses as a function of composition has been explained based on the change in the relative concentration of BO 4 and BO 3 structural units. These glasses in the powder form can act as efficient room temperature ion exchangers for metal ions like Cu 2+ . It is seen that the ion exchange does not affect the boron and silicon structural units as revealed by IR studies.