Autor(es)

Salmon, Philip S. ; Lange, Esther Giron ; Zeidler, Anita ; Bradtmueller, Henrik ; Ensuncho, Laureano ; Cuello, Gabriel J. ; Eckert, Hellmut

• Tipo de documento: Artigo Científico
• Fonte: Journal of Chemical Physics; v. 163, n. 14, p. 17-pg., 2025-10-14.

Resumo

The structure of (Nb2O5)(x)(NaPO3)(1-x) glasses was re-visited by combining neutron and high energy x-ray diffraction with Raman scattering over a wide composition range. The results were interpreted by reference to the phosphorus atom speciation found from a novel analysis of P-31 magic angle spinning nuclear magnetic resonance spectra [Ensuncho et al., J. Am. Chem. Soc. 147, 31147 (2025)]. The results indicate a distorted octahedral coordination environment for the Nb atoms across the composition range. The measured x-dependence of (i) the mean numbers of non-bridging oxygen (NBO) atoms and P-O-P and P-O-Nb connections per phosphate group, and (ii) the fraction of oxygen atoms in Nb-O-Nb connections, are described by a self-consistent analytical model in which there is a preferential formation of heteronuclear P-O-Nb bonds within a network structure formed by 4- and 6-coordinated P and Nb atoms, respectively, such that P-O-P connections are absent when the niobia content exceeds x similar to 0.22. At smaller x, the non-bridging oxygen atoms are distributed among the P- and Nb-centered polyhedral units. The model provides a connectivity density that accounts for the rapid increase in the glass transition temperature with increasing Nb2O5 content and shows that the enhancement to the non-linear optical properties for x > 0.2 is related to a more rapid increase with x in the fraction of oxygen atoms involved in polarizable Nb-O-Nb connections. The methodology also suggests that the dissolution rate measured for the (Nb2O5)(x)(Na2O)(0.4)(P2O5)(0.6-x) glass series is dependent on the proportion of P-O-P linkages. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial 4.0International (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/).https://doi.org/10.1063/5.0290349 (AU)

• Processo FAPESP: 22/14232-0 - Titânio e nióbio: Dois elementos importantes, mas enigmáticos na ciência do vidro
• Beneficiário: Hellmut Eckert
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 22/01937-5 - Incorporação do nióbio em vidros fotônicos: Novas Relações estruturais/funções descobertas por técnicas avançadas de ressonância magnética.
• Beneficiário: Laureano Javier Ensuncho Hernández
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 19/26399-3 - Elucidação de rearranjos estruturais durante o processo de relaxação e cristalização de materiais vítreos
• Beneficiário: Henrik Bradtmüller
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 13/07793-6 - CeRTEV - Centro de Pesquisa, Tecnologia e Educação em Materiais Vítreos
• Beneficiário: Edgar Dutra Zanotto
• Modalidade de apoio: Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs