A-Site Doping Enables Stabilization and Migration of Oxygen Vacancies in Langasite Frameworks

Yang Chen; Zhaoji Luo; Xiaohui Li; Cheng Li; Sihao Deng; Lunhua He; Qiang Li; Xianran Xing; Xiaojun Kuang

doi:10.1002/sstr.202500633

A-Site Doping Enables Stabilization and Migration of Oxygen Vacancies in Langasite Frameworks

Yang Chen
, Zhaoji Luo
, Xiaohui Li
, Cheng Li
, Sihao Deng
, Lunhua He
, Qiang Li
, Xianran Xing
, Xiaojun Kuang

Powder Diffraction

Research output: Contribution to journal › Article › peer-review

Abstract

Open-framework oxides are promising oxide-ion conducting candidates for next-generation solid oxide fuel cells (SOFCs) owing to their ability to accommodate and transport oxygen defects. Here, we demonstrate that strategic A-site substitution with Sr²⁺ in the langasite framework La_3-xSr_xGa₅GeO_14-x/2 effectively introduces oxygen-vacancy migration, with enhanced oxide-ion conductivity of 3.08 × 10⁻⁴ S/cm at 1000°C. Neutron powder diffraction (NPD), pair distribution function (PDF) analysis combined with reverse Monte Carlo (RMC) modeling, and static lattice calculations, reveal that oxygen vacancies induced by Sr doping were stabilized by local structural relaxation involving only the surrounding GaO₄ units transforming into GaO₅ coordination environments through edge-sharing, whereas GaO₆ units and GeO₄ units largely preserve their original geometries. Complementary bond valence site energy calculations and molecular dynamics simulations further uncover the migration mechanism, revealing that oxide-ion transport proceeds predominantly through two-dimensional long-range diffusion within the ab plane, with dynamic participation of all the crystallographic oxygen sites. This work establishes A-site doping in langasites as a viable route for stabilizing oxygen defects and promoting their migration, offering fundamental insights into the design of high-performance oxide-ion conductors.

Original language	English
Article number	e202500633
Journal	Small Structures
Volume	7
Issue number	1
DOIs	https://doi.org/10.1002/sstr.202500633
State	Published - Jan 2026

Funding

This study was supported by the Natural Science Foundation of Guangxi Province (2025GXNSFBA069588), Guangxi Key Research & Development Program (GuikeAB25069467), National Natural Science Foundation of China (22205017, 22575063, 22090043, 22090042), National Key R&D Program of China (2020YFA0406202), and Guilin university of Technology Research Startup Project (RD2400002912). This research was supported by the Guangxi Natural Science Foundation (No. 2025GXNSFBA069588), Guangxi Key Research & Development Program (No. GuikeAB25069467), National Natural Science Foundation of China (Nos. 22205017, 22575063, 22090043, 22090042), the National Key R&D Program of China (2020YFA0406202), Guilin university of Technology Research Startup Project (NO. RD2400002912). The authors are grateful to Guangxi BaGui Scholars Special Funding.

Keywords

defect chemistry
langasite frameworks
oxide-ion conductors
oxygen-vacancy stabilization and migration mechanisms

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10.1002/sstr.202500633

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title = "A-Site Doping Enables Stabilization and Migration of Oxygen Vacancies in Langasite Frameworks",

abstract = "Open-framework oxides are promising oxide-ion conducting candidates for next-generation solid oxide fuel cells (SOFCs) owing to their ability to accommodate and transport oxygen defects. Here, we demonstrate that strategic A-site substitution with Sr2+ in the langasite framework La3-xSrxGa5GeO14-x/2 effectively introduces oxygen-vacancy migration, with enhanced oxide-ion conductivity of 3.08 × 10−4 S/cm at 1000°C. Neutron powder diffraction (NPD), pair distribution function (PDF) analysis combined with reverse Monte Carlo (RMC) modeling, and static lattice calculations, reveal that oxygen vacancies induced by Sr doping were stabilized by local structural relaxation involving only the surrounding GaO4 units transforming into GaO5 coordination environments through edge-sharing, whereas GaO6 units and GeO4 units largely preserve their original geometries. Complementary bond valence site energy calculations and molecular dynamics simulations further uncover the migration mechanism, revealing that oxide-ion transport proceeds predominantly through two-dimensional long-range diffusion within the ab plane, with dynamic participation of all the crystallographic oxygen sites. This work establishes A-site doping in langasites as a viable route for stabilizing oxygen defects and promoting their migration, offering fundamental insights into the design of high-performance oxide-ion conductors.",

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author = "Yang Chen and Zhaoji Luo and Xiaohui Li and Cheng Li and Sihao Deng and Lunhua He and Qiang Li and Xianran Xing and Xiaojun Kuang",

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AU - Chen, Yang

AU - Luo, Zhaoji

AU - Li, Xiaohui

AU - Li, Cheng

AU - Deng, Sihao

AU - He, Lunhua

AU - Li, Qiang

AU - Xing, Xianran

AU - Kuang, Xiaojun

PY - 2026/1

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N2 - Open-framework oxides are promising oxide-ion conducting candidates for next-generation solid oxide fuel cells (SOFCs) owing to their ability to accommodate and transport oxygen defects. Here, we demonstrate that strategic A-site substitution with Sr2+ in the langasite framework La3-xSrxGa5GeO14-x/2 effectively introduces oxygen-vacancy migration, with enhanced oxide-ion conductivity of 3.08 × 10−4 S/cm at 1000°C. Neutron powder diffraction (NPD), pair distribution function (PDF) analysis combined with reverse Monte Carlo (RMC) modeling, and static lattice calculations, reveal that oxygen vacancies induced by Sr doping were stabilized by local structural relaxation involving only the surrounding GaO4 units transforming into GaO5 coordination environments through edge-sharing, whereas GaO6 units and GeO4 units largely preserve their original geometries. Complementary bond valence site energy calculations and molecular dynamics simulations further uncover the migration mechanism, revealing that oxide-ion transport proceeds predominantly through two-dimensional long-range diffusion within the ab plane, with dynamic participation of all the crystallographic oxygen sites. This work establishes A-site doping in langasites as a viable route for stabilizing oxygen defects and promoting their migration, offering fundamental insights into the design of high-performance oxide-ion conductors.

AB - Open-framework oxides are promising oxide-ion conducting candidates for next-generation solid oxide fuel cells (SOFCs) owing to their ability to accommodate and transport oxygen defects. Here, we demonstrate that strategic A-site substitution with Sr2+ in the langasite framework La3-xSrxGa5GeO14-x/2 effectively introduces oxygen-vacancy migration, with enhanced oxide-ion conductivity of 3.08 × 10−4 S/cm at 1000°C. Neutron powder diffraction (NPD), pair distribution function (PDF) analysis combined with reverse Monte Carlo (RMC) modeling, and static lattice calculations, reveal that oxygen vacancies induced by Sr doping were stabilized by local structural relaxation involving only the surrounding GaO4 units transforming into GaO5 coordination environments through edge-sharing, whereas GaO6 units and GeO4 units largely preserve their original geometries. Complementary bond valence site energy calculations and molecular dynamics simulations further uncover the migration mechanism, revealing that oxide-ion transport proceeds predominantly through two-dimensional long-range diffusion within the ab plane, with dynamic participation of all the crystallographic oxygen sites. This work establishes A-site doping in langasites as a viable route for stabilizing oxygen defects and promoting their migration, offering fundamental insights into the design of high-performance oxide-ion conductors.

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KW - oxygen-vacancy stabilization and migration mechanisms

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A-Site Doping Enables Stabilization and Migration of Oxygen Vacancies in Langasite Frameworks

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