Four and six-coordinated Al in a fluorite-type structure: A key to the stabilization of Sc2O3-stabilized ZrO2

IF 3.3 4区材料科学 Q3 CHEMISTRY, PHYSICAL

Solid State Ionics Pub Date : 2025-08-27 DOI:10.1016/j.ssi.2025.116997

Itaru Oikawa , Akihiro Fujimaki , Akihiro Ishii , Fuminori Tamazaki , Hiroshi Okamoto , Hitoshi Takamura

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引用次数: 0

Abstract

Al is known as a unique element to enhance the stability of Sc₂O₃-stabilized ZrO₂ (ScSZ); however, understanding the Al state in the material is insufficient for the mechanism to be understood. In this study, the states and roles of Al in the ScSZ-based materials are elucidated by ²⁷Al NMR spectroscopy, DFT calculations, and detailed structural analysis concerning cubicity. The ²⁷Al NMR and DFT calculations reveal that Al substitutes Zr sites as 6-, 7- and 8-coordinated states in ScSZ even though the ionic radius of Al is much smaller than that of Zr. The formation of 6-coordinated Al with two oxygen vacancies in its vicinity indicates oxygen vacancies are preferentially located around the smaller cations. The local structure revealed by DFT calculations suggests that the coordination polyhedron of 7- and 8-coordinated Al is effectively 4-coordinated Al. The ²⁷Al NMR results also support this unique local structure. The results of this study show that manipulating the Al state is a key step in stabilizing Sc₂O₃-stabilized ZrO₂ and help to clarify the suppression mechanism of the degradation of conductivity.

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萤石型结构中的四和六配位铝：稳定sc2o3稳定ZrO2的关键

Al被认为是增强sc2o3稳定ZrO2 （ScSZ）稳定性的独特元素；然而，仅了解材料中的Al态还不足以理解其机理。在本研究中，通过27Al核磁共振谱、DFT计算和详细的立方度结构分析，阐明了Al在scz基材料中的状态和作用。27Al核磁共振和DFT计算表明，尽管Al的离子半径远小于Zr，但在ScSZ中，Al取代了Zr的6、7和8配位态。6配位铝在其附近形成两个氧空位，表明氧空位优先位于较小的阳离子周围。DFT计算揭示的局部结构表明，7-和8-配位Al的配位多面体是有效的4-配位Al。27Al核磁共振结果也支持这种独特的局部结构。本研究结果表明，控制Al态是稳定sc2o3稳定ZrO2的关键步骤，有助于阐明电导率退化的抑制机制。

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来源期刊

Solid State Ionics 物理-物理：凝聚态物理

CiteScore

6.10

自引率

3.10%

发文量

152

审稿时长

58 days

期刊介绍： This interdisciplinary journal is devoted to the physics, chemistry and materials science of diffusion, mass transport, and reactivity of solids. The major part of each issue is devoted to articles on: (i) physics and chemistry of defects in solids; (ii) reactions in and on solids, e.g. intercalation, corrosion, oxidation, sintering; (iii) ion transport measurements, mechanisms and theory; (iv) solid state electrochemistry; (v) ionically-electronically mixed conducting solids. Related technological applications are also included, provided their characteristics are interpreted in terms of the basic solid state properties. Review papers and relevant symposium proceedings are welcome.