| Texto completo | |
| Autor(es): |
Morguetto, Gabriel Felipe
;
de Oliveira Junior, Marcos
;
Schneider, Jose Fabian
;
Eckert, Hellmut
Número total de Autores: 4
|
| Tipo de documento: | Artigo Científico |
| Fonte: | Journal of Physical Chemistry C; v. 125, n. 8, p. 13-pg., 2021-02-22. |
| Resumo | |
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 center dot xLi(2)O}center dot ySrO center dot 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 P-3(1), Li-6, Li-7, and Cs-133. As Sr is introduced, the molar volume and P-31 NMR parameters indicate a monotonic structural evolution, while nonadditive behaviors are noticed in the glasstransition temperature. The behavior of Li-7 and Cs-133 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 Li-7 - Li-7 and the heteronuclear Li-7-Cs-1(33) magnetic dipole dipolar couplings, the latter of which were selectively measured by Li-7{Cs-133} 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. (AU) | |
| Processo FAPESP: | 13/07793-6 - CEPIV - Centro de Ensino, Pesquisa e Inovação em Vidros |
| Beneficiário: | Edgar Dutra Zanotto |
| Modalidade de apoio: | Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs |
| Processo FAPESP: | 19/12885-3 - EMU concedido no processo 2013/07793-6: espectrômetro de ressonância magnética nuclear em estado sólido |
| Beneficiário: | José Fabián Schneider |
| Modalidade de apoio: | Auxílio à Pesquisa - Programa Equipamentos Multiusuários |