| The Si('29) nuclear magnetic resonance spectra for glasses and polycrystalline materials in the potassium silicate system have been observed. An anisotropic chemical shift is present in these materials and the first ever detections of these shifts are presented. Resultant NMR lineshapes for materials at selected compositions are correlated with the structural groupings proposed as present in both glasses and crystalline materials.;The NMR spectra for B('11) in glasses of the Li(,2)O-TeO(,2)-B(,2)O(,3) and TeO(,2)-B(,2)O(,3)-Al(,2)O(,3) systems were secured and used to study the behavior of N(,4), the fraction of boron atoms in four-coordination, as a function of glass composition. The appearance of non-zero values for N(,4) in the TeO(,2)-B(,2)O(,3)-Al(,2)O(,3) glasses and the enhancement of N(,4) in the Li(,2)O-TeO(,2)-B(,2)O(,3) glasses above that obtained for the binary Li(,2)O-B(,2)O(,3) glass system indicates that the TeO(,2) in the glasses contributes to the formation of four-coordinated boron atoms. A mechanism which accounts for the N(,4) behavior is presented. Relations describing the behavior of N(,4) for the binary TeO(,2)-B(,2)O(,3) system are inferred from the results secured.;The B('11) NMR spectra in several zinc borate crystalline compounds and glasses have been used to study the structures present in these materials. The NMR spectra in conjunction with computer-generated spectra were used to make structural inferences for these materials. Correlations are made between the structures found using NMR and the crystalline structures proposed in the literature for these materials. Zinc borate glasses spanning the reported glass formation range were studied and values for N(,4) in the glasses are given. |
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