Covalency and Lone Pair-Driven Distortions in Sulfur-Doped Tin Niobate

Publication Title

Inorganic Chemistry

Document Type

Article

Department or Program

Chemistry

Publication Date

8-27-2025

Abstract

Heteroanionic materials can provide a powerful platform for tuning the local structure and electronic properties through targeted chemical substitution. Among them, heteroanionic pyrochlores offer exceptional flexibility due to their robust framework and capacity to host both cation and anion disorders. In this study, we investigate the structure–property relationship in sulfur-doped tin niobate Sn2Nb2O7-xSx, a lone pair-active pyrochlore where substitution of sulfur into the O′ site systematically modulates both the electronic structure and local coordination environments. By combining synchrotron and neutron total scattering, we demonstrated that the appropriate local structure of sulfur-doped tin niobate is the P212121space group. This lower-symmetry model captures site-specific displacements that are not permitted in the high-symmetry cubic Fd3̅m average structure. Our results show that increasing sulfur concentration suppresses distortions by reducing the stereochemical activity of the Sn2+lone pair while simultaneously enhancing local distortion near S-substituted sites. Band gap measurements and structural trends suggest a strong correlation among sulfur concentration, lone pair suppression, and optical behavior. Heteroanionic pyrochlores emerge as a versatile platform for tuning the local symmetry and electronic structure via lone pair–anion interactions, thereby offering alternative synthetic routes for structure–property control.

Comments

Original version is available from the publisher at: https://doi.org/10.1021/acs.inorgchem.5c03653

PubMed ID

40867033

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