Abstract
Magic angle spinning nuclear magnetic resonance (MAS NMR) is used to measure the 29Si chemical shift and full width at half maximum in Na2O·2SiO2·xMnO for 0.0≤x≤0.8 glasses. The large space varying magnetic field of the paramagnetic centers increases the line width and moves the chemical shift to a lower frequency, i.e. more shielded, with the increase of Mn++. The T1 relaxation time falls rapidly and the relaxation rate is shown to be proportional with the concentration of MnO. The differential thermal analysis (DTA) results show that the glass transition temperature, Tg, crystallization temperature, Tx, and liquidus temperature TL do not change due to addition of MnO. This suggests that Mn++ does not form chemical bond with the network. However, the Mn++ acts as nucleating agent and enhances the crystallization and the rate of crystallization can be tailored by judicious choice of the amount of MnO.
Published Version
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