Probing the validity of the spinel inversion model: a combined SPXRD, PDF, EXAFS and NMR study of ZnAl2O4.,Dalton Transactions

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Probing the validity of the spinel inversion model: a combined SPXRD, PDF, EXAFS and NMR study of ZnAl2O4.
Dalton Transactions ( IF 3.5 ) Pub Date : 2020-09-23 , DOI: 10.1039/d0dt02795b
Sanna Sommer ₁ , Espen Drath Bøjesen , Nina Lock , Hidetaka Kasai , Jørgen Skibsted , Eiji Nishibori , Bo Brummerstedt Iversen

Affiliation

Spinels are of essential interest in the solid-state sciences with numerous important materials adopting this crystal structure. One defining feature of spinel compounds is their ability to accommodate a high degree of tailorable point defects, and this significantly influences their physical properties. Standard defect models of spinels often only consider metal atom inversion between octahedral and tetrahedral sites, thereby neglecting other defects such as interstitial atoms. In addition, most studies rely on a single structural characterization technique, and this may bias the result and give uncertainty about the correct crystal structure. Here we explore the virtues of multi-technique investigations to limit method and model bias. We have used Pair Distribution Function analysis, Rietveld refinement and Maximum Entropy Method analysis of Powder X-ray Diffraction data, Zn edge Extended X-ray Absorption Fine Structure, and solid-state ²⁷Al Nuclear Magnetic Resonance to study the structural defects in ZnAl₂O₄ spinel samples prepared by either microwave hydrothermal synthesis, supercritical flow synthesis, or spark plasma sintering. In addition, the samples were subjected to thermal post treatments. The study demonstrates that numerous synthesis dependent defects are present and that the different synthesis pathways allow for defect tailoring within the ZnAl₂O₄ structure. This suggests a pathway forward for optimization of the physical properties of spinel materials.

中文翻译：

探索尖晶石反演模型的有效性：ZnAl2O4的SPXRD，PDF，EXAFS和NMR组合研究。

尖晶石在固态科学中至关重要，许多重要材料都采用这种晶体结构。尖晶石化合物的一个定义特征是其适应高度可定制的点缺陷的能力，这会极大地影响其物理性能。尖晶石的标准缺陷模型通常仅考虑八面体和四面体位点之间的金属原子倒置，从而忽略了诸如间隙原子之类的其他缺陷。此外，大多数研究都依赖于单一的结构表征技术，这可能会使结果产生偏差，并给正确的晶体结构带来不确定性。在这里，我们探索了多种技术研究的优点，以限制方法和模型偏差。我们使用了结对分布函数分析，²⁷ Al核磁共振，研究通过微波水热合成，超临界流合成或火花等离子体烧结制备的ZnAl₂ O₄尖晶石样品的结构缺陷。另外，对样品进行热后处理。研究表明存在大量依赖于合成的缺陷，并且不同的合成途径允许在ZnAl₂ O₄结构内进行缺陷定制。这表明优化尖晶石材料物理性能的途径。

更新日期：2020-10-06

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