Sommer Sanna, Bøjesen Espen Drath, Lock Nina, Kasai Hidetaka, Skibsted Jørgen, Nishibori Eiji, Iversen Bo Brummerstedt
Center for Materials Crystallography, Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Langelandsgade 140, 8000-DK Aarhus, Denmark.
Dalton Trans. 2020 Oct 6;49(38):13449-13461. doi: 10.1039/d0dt02795b.
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.
尖晶石在固态科学领域至关重要，许多重要材料都采用这种晶体结构。尖晶石化合物的一个显著特征是它们能够容纳高度可定制的点缺陷，这对其物理性质有重大影响。尖晶石的标准缺陷模型通常只考虑八面体和四面体位置之间的金属原子反转，从而忽略了其他缺陷，如间隙原子。此外，大多数研究依赖单一的结构表征技术，这可能会使结果产生偏差，并导致对正确晶体结构的不确定性。在此，我们探索采用多种技术进行研究的优点，以减少方法和模型偏差。我们利用粉末X射线衍射数据的对分布函数分析、Rietveld精修和最大熵方法分析、锌边扩展X射线吸收精细结构以及固态27Al核磁共振来研究通过微波水热合成、超临界流合成或放电等离子烧结制备的ZnAl2O4尖晶石样品中的结构缺陷。此外，对样品进行了热后处理。研究表明存在许多与合成相关的缺陷，并且不同的合成途径能够在ZnAl2O4结构内实现缺陷定制。这为优化尖晶石材料的物理性质指明了一条前进的道路。
