B11 NMR studies of MnO-B2O3 glass system

Nuclear magnetic resonance (NMR) technique have been employed to investigate the environment of boron as a function of composition in the paramagnetic MnO-B2O3 glass system. B11 NMR spectra in the glasses exhibit the presence of both magnetic shift and nuclear electric quadrupole effects. The behavior of N4 data are quite similar to those for the borate glasses modified by alkali ions. Below, 0.4 molar fraction of MnO, the glasses are viewed as a random network of the structural groupings that occur in the crystalline MnO x 3B2O3 and MnO x 2B2O3 compounds. However, above 0.4 molar fraction of MnO, nonbridging oxygens are formed by destruction of the BO4 tetrahedra due to extra oxygens. (author)