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Structure and red–ox chemistry of tin in SnO·$NaPO_3$ pseudo-binary glasses

Bhat, Harish M and Berry, FJ and Jiang, JZ and Rao, KJ (2001) Structure and red–ox chemistry of tin in SnO·$NaPO_3$ pseudo-binary glasses. In: Journal of Non-Crystalline Solids, 291 (1-2). pp. 93-106.

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Thermal and spectroscopic investigations have been carried out on a number of binary $SnO–N_aPO_3$ glasses over a wide range of compositions; $SnO:NaPO_3$ from 0:100 to 45:55. Structures of the glasses have been investigated using Raman, Fourier transform infrared (FTIR), $^{31}P-HR-MAS-NMR$ and $^{119}Sn$ Mössbauer spectroscopies. $^{119}Sn$ Mössbauer spectra suggests that there is an equilibrium of $Sn^{II}(SnO)$ and $Sn^{IV}(SnO_2)$ in the glasses in the ratio 40:60 irrespective of the composition. $^{31}P-MAS-NMR$, IR and Raman spectra confirm the partial oxidation of SnO to $SnO_2$. The unoxidized part of SnO in the glass acts as a modifier up to $\sim27$ mol% of nominal composition. Above this concentration, SnO acts as a glass former. $SnO_2$ however, is always found to behave as a glass network former. A structural model has been proposed, which envisages $Sn^{IV}$ as playing a key role in preserving part of the metaphosphate units in the structure so that SnO changes its role from a modifier to former above 27 mol% (SnO) concentration. The model is consistent with the behaviour of glass transition temperatures, molar volumes and compositional dependence of infrared (IR) and Raman spectroscopic features. The equilibration of $Sn^{II}$ and $Sn^{IV}$ in the phosphate glasses is rationalized on the basis of a kinetic approach, which visualizes the presence of a pre-equilibrium situation where the slow step is the transfer of $O^2$ to the phosphate matrix from the dissolved $O^2_2$ species.

Item Type: Journal Article
Publication: Journal of Non-Crystalline Solids
Publisher: Elsevier
Additional Information: Copyright of this article belongs to Elsevier.
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 07 Jun 2006
Last Modified: 19 Sep 2010 04:29
URI: http://eprints.iisc.ac.in/id/eprint/7546

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