• V C Veeranna Gowda

      Articles written in Bulletin of Materials Science

    • Elastic properties and spectroscopic studies of Na2O–ZnO–B2O3 glass system

      V C Veeranna Gowda R V Anavekar

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      Elastic properties, 11B MAS–NMR and IR spectroscopic studies have been employed to study the structure of Na2O–ZnO–B2O3 glasses. Sound velocities and elastic moduli such as longitudinal, Young’s, bulk and shear modulus have been measured at a frequency of 10 MHz as a function of ZnO concentration. Both sound velocities and elastic moduli increase with increasing ZnO concentration. Poisson’s ratio and Debye temperature were also found to increase with ZnO concentration. 11B MAS–NMR and IR spectra show characteristic features of borate network and compositional dependence trends as a function of Na2O/ZnO concentration. The results are discussed in view of borate network and dual structural role of Zn2+ ion into the network. The results indicate that the Zn2+ ions are likely to occupy network forming positions in this glass system.

    • A new approach for understanding ion transport in glasses; example of complex alkali diborate glasses containing lead, bismuth and tellurium oxides

      V C Veeranna Gowda C Narayana Reddy K J Rao

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      Mechanism of ion transport in glasses continues to be incompletely understood. Several of the theoretical models in vogue fail to rationalize conductivity behaviour when d.c. and a.c. measurements are considered together. While they seem to involve the presence of at least two components in d.c. activation energy, experiments fail to reveal that feature. Further, only minor importance is given to the influence of structure of the glass on the ionic conductivity behaviour. In this paper, we have examined several general aspects of ion transport taking the example of ionically conducting glasses in pseudo binary, 𝑦Na2B4O7.(1−𝑦) M$_{a}$O$_{b}$ (with 𝑦 = 0.25–0.79 and M$_{a}$O$_{b}$ = PbO, TeO2 and Bi2O3) system of glasses which have also been recently characterized. Ion transport in them has been studied in detail. We have proposed that non-bridging oxygen (NBO) participation is crucial to the understanding of the observed conductivity behaviour. NBO–BO switching is projected as the first important step in ion transport and alkali ion jump is a subsequent event with a characteristically lower barrier which is, therefore, not observed in any study. All important observations in d.c. and a.c. transport in glasses are found consistent with this model.

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