Characterization and structural developments of gel-derived borosilicate glasses: a multinuclear MAS-NMR study

Abstract Twelve different homogeneous sodium borosilicate glasses were prepared by the alkoxide-gel method. To study the development from the dried gel to the glass and the structure of the final product, after annealing at various temperatures 11 B, 29 Si, 1 H and 23 Na MAS-NMR methods have been applied in a magnetic field of 7 T. Chemical shifts and quadrupole parameters have been measured and related to the structure. Condensation, copolymerization and removal of hydrogen-containing groups have been observed. With one exception where phase separation occurred, all the glasses appeared to be homogeneous. In contrast to molten glasses, they have been modeled by a uniform distribution of copolymerized SiO 4 , BO 3 and BO 4 polyhedra. Relationships between the isotropic chemical shifts and the composition of the materials have been obtained.