Structural Role of Nb 2 O 5 in Phosphate Glasses: An Advanced Solid-State NMR Protocol for the Glass System x Nb 2 O 5 –(100– x )NaPO 3
Year: 2025
Type: article
Abstract: The structural role of Nb 2 O 5 in oxide glasses remains poorly understood, despite the unique linear and nonlinear optical properties that it bestows. Here, advanced solid-state NMR methods can yield valuable insight, but their full potential has been underutilized for niobium-containing systems, especially in respect of the dipolar techniques that provide quantitative information on the interatomic connectivity and distance distributions. This study presents a new NMR-strategy and applies it to the model glass system x Nb 2 O 5 –(100– x )NaPO 3 (0 ≤ x ≤ 40). The number of P–O–P linkages per P atom is estimated from the 31 P– 31 P dipole–dipole interactions using spin echo decay (SED) and double-quantum based dipolar recoupling effecting nuclear alignment reduction (DQ-DRENAR). The number of P–O–Nb linkages is obtained from the 31 P– 93 Nb dipolar coupling using 93 Nb{ 31 P} rotational echo double resonance (REDOR) and, for the first time, 31 P{ 93 Nb} rotational echo saturation pulse double resonance (RESPDOR). Constrained by these interaction-selective experiments, which also include 31 P/ 23 Na double resonance spectroscopy, the poorly resolved 31 P MAS NMR spectra are quantitatively decomposed into their contributions from the various network-forming units. Additional field dependent 93 Nb MAS NMR experiments provide chemical shift parameters that reveal multiple six-coordinate niobium environments with varying degrees of distortion. Overall, the results demonstrate that Nb 2 O 5 assumes a network former role, increasing the overall network connectivity. They also demonstrate an advanced solid-state NMR protocol for characterizing the structural role of Nb 2 O 5, an important intermediate oxide, in multicomponent glasses.
DOI: 10.1021/jacs.5c09793
Language: English
Subfield: Ceramics and Composites
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W4413279360