| Texto completo | |
| Autor(es): |
Sen, Sabyasachi
;
Lancelotti, Ricardo F.
;
Hung, Ivan
;
Gan, Zhehong
Número total de Autores: 4
|
| Tipo de documento: | Artigo Científico |
| Fonte: | Journal of Physical Chemistry B; v. 128, n. 11, p. 10-pg., 2024-03-11. |
| Resumo | |
The Pb-O coordination environment in binary (PbO)(x)(SiO2)(100-x) glasses with 30 <= x <= 70 is probed by using two-dimensional Pb-207 nuclear magnetic resonance (NMR) isotropic-anisotropic correlation spectroscopy. The isotropic Pb-207 NMR spectra show little composition-dependent evolution of the Pb-O nearest-neighbor coordination environment. The systematic variation of the chemical shift tensor parameters offers a unique insight into their local site symmetry and suggests the presence of pyramidal PbO3 and PbO4 sites with sterically active electron lone pairs and with Pb-O bond lengths ranging between 0.23 and 0.25 nm. The PbO3/PbO4 ratio shows a small but monotonic increase from similar to 70:30 to 80:20 as the PbO content increases from 30 to 70 mol %. When taken together, the isotropic and anisotropic Pb-207 NMR spectra suggest that the majority of the PbOn (3 <= n <= 4) pyramids in these glasses are connected to the SiO4 tetrahedra via Pb-O-Si linkages. A significant fraction of Pb-O-Pb linkages, where the oxygen is linked only to Pb atoms, appears only in glasses with PbO >= 60 mol %. These oxygen atoms appear to be corner-shared between the PbOn pyramids in the structure, and no evidence for edge-sharing between these pyramids is observed in this composition range. We hypothesize that a substantial fraction of the constituent PbOn pyramids start to participate in edge-sharing only at higher PbO contents (>70 mol %), which diminishes the glass-forming ability of the network. This work illustrates the potential of isotropic-anisotropic correlation NMR spectroscopy in structural studies involving nuclides with large chemical shift ranges and anisotropy. (AU) | |
| Processo FAPESP: | 22/07679-8 - Origem em escala atômica da relaxação estrutural de vidros metassilicato de chumbo e dissilicato de lítio |
| Beneficiário: | Ricardo Felipe Lancelotti |
| Modalidade de apoio: | Bolsas no Exterior - Estágio de Pesquisa - Doutorado |