DTA, powder XRD and SEM study of manganese-containing borate glasses

Several homogeneous glasses in the ternary SiO2/B2O3/Na2O containing MnO2 were investigated by powder XRD, DTA and SEM. The presence of a crystalline Mn7SiO12 phase in the glasses which contain more than 20 mol% of MnO2 is confirmed. The crystalline compound could be synthesised in a pure form at 1000°C at ambient pressure. No other crystalline phase in the ternary Si---Mn---O was detected in the otherwise homogeneous glass.