Mixed Cs-Li-Sr metaphosphate glasses. MORGUETTO, Gabriel Felipe; OLIVEIRA JUNIOR, Marcos de; SCHNEIDER, José Fabian; ECKERT, Hellmut.
Abstract: Li-Cs metaphosphate glasses show one of the strongest mixed ion effects (MIE) known in d.c. conductivity. Previous studies had shown that the ions in these glasses are randomly distributed relative to each other. For such random distributions, the restriction on the ionic transport can be understood to result from an effective blockage of the diffusion pathways for each ionic species caused by the presence of structural sites adapted to the other species, rendering successful ion jumps between mismatched sites unlikely. In the present work, we probed the behavior of the ion mixture after the introduction of a third species, Sr, in the metaphosphate system (0.5 - y){(1 - x)Cs2O·xLi2O}·ySrO·0.5 P2O5, with 0 = y = 0.40 and three fixed values for the Cs-to-Li replacement ratio x = [Li]/([Li] + [Cs]) = 0.25, 0.50, and 0.75. The structural aspects regarding the local environments and the spatial distribution of the cations were analyzed using nuclear magnetic resonance techniques for 31P, 6Li, 7Li, and 133Cs. As Sr is introduced, the molar volume and 31P NMR parameters indicate a monotonic structural evolution, while nonadditive behaviors are noticed in the glass-transition temperature. The behavior of 7Li and 133Cs NMR parameters is consistently correlated with the respective alkali atom density, regardless of the level of Sr incorporation or the Li/Cs + Li substitution ratio. A systematic increase in the average Cs-O distances is observed as Cs is replaced either by Li or Sr. Similar linear correlations are observed for the second moments characterizing the homonuclear 7Li-7Li and the heteronuclear 7Li-133Cs magnetic dipole dipolar couplings, the latter of which were selectively measured by 7Li{133Cs} spin echo double resonance (SEDOR) technique. Altogether, these results are consistent with random mixing of Li, Cs, and Sr modifier cations in the glass structure.
Journal of Physical Chemistry C
v. 125, n. 8, p. 4764-4776 + supporting information: S1-S3 - Ano: 2021
Fator de Impacto: 4,189
@article={003022170,author = {MORGUETTO, Gabriel Felipe; OLIVEIRA JUNIOR, Marcos de; SCHNEIDER, José Fabian; ECKERT, Hellmut.},title={Mixed Cs-Li-Sr metaphosphate glasses},journal={Journal of Physical Chemistry C},note={v. 125, n. 8, p. 4764-4776 + supporting information: S1-S3},year={2021}}
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Abstract: Li-Cs metaphosphate glasses show one of the strongest mixed ion effects (MIE) known in d.c. conductivity. Previous studies had shown that the ions in these glasses are randomly distributed relative to each other. For such random distributions, the restriction on the ionic transport can be understood to result from an effective blockage of the diffusion pathways for each ionic species caused by the presence of structural sites adapted to the other species, rendering successful ion jumps between mismatched sites unlikely. In the present work, we probed the behavior of the ion mixture after the introduction of a third species, Sr, in the metaphosphate system (0.5 - y){(1 - x)Cs2O·xLi2O}·ySrO·0.5 P2O5, with 0 = y = 0.40 and three fixed values for the Cs-to-Li replacement ratio x = [Li]/([Li] + [Cs]) = 0.25, 0.50, and 0.75. The structural aspects regarding the local environments and the spatial distribution of the cations were analyzed using nuclear magnetic resonance techniques for 31P, 6Li, 7Li, and 133Cs. As Sr is introduced, the molar volume and 31P NMR parameters indicate a monotonic structural evolution, while nonadditive behaviors are noticed in the glass-transition temperature. The behavior of 7Li and 133Cs NMR parameters is consistently correlated with the respective alkali atom density, regardless of the level of Sr incorporation or the Li/Cs + Li substitution ratio. A systematic increase in the average Cs-O distances is observed as Cs is replaced either by Li or Sr. Similar linear correlations are observed for the second moments characterizing the homonuclear 7Li-7Li and the heteronuclear 7Li-133Cs magnetic dipole dipolar couplings, the latter of which were selectively measured by 7Li{133Cs} spin echo double resonance (SEDOR) technique. Altogether, these results are consistent with random mixing of Li, Cs, and Sr modifier cations in the glass structure.
@article={003022170,author = {MORGUETTO, Gabriel Felipe; OLIVEIRA JUNIOR, Marcos de; SCHNEIDER, José Fabian; ECKERT, Hellmut.},title={Mixed Cs-Li-Sr metaphosphate glasses},journal={Journal of Physical Chemistry C},note={v. 125, n. 8, p. 4764-4776 + supporting information: S1-S3},year={2021}}