Santucci Simone, Zhang Haiwu, Kabir Ahsanul, Marini Carlo, Sanna Simone, Han Jyn Kyu, Ulbrich Gregor, Heppke Eva Maria, Castelli Ivano E, Esposito Vincenzo
Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs., Lyngby, Denmark.
ALBA Synchrotron, Carrer de la llum, 2-26Cerdanyola del Vallès, 08290 Barcelona, Spain.
Phys Chem Chem Phys. 2021 May 19;23(19):11233-11239. doi: 10.1039/d1cp00748c.
Oxygen-defective ceria, e.g. Gd-doped ceria, shows giant electromechanical properties related to a complex local rearrangement of its lattice. Although they are not entirely identified, the electroactive mechanisms arise from cation and oxygen vacancy (VO) pairs (i.e. Ce-VO), and the local structural elastic distortion in their surroundings. Here, we study the geometry and behaviour of Ce-VO pairs in a grain boundary-free bulk Ce0.9Gd0.1O1.95 single crystal under an AC electric field of ca. 11 kV cm-1. The analysis was carried out through X-ray absorption spectroscopy (XAS) techniques at the Ce L-III edge. Using Density Functional Theory (DFT) calculations, we investigated the effects of the strain on density of states and orbitals at the valence band edge. Our research indicates that electrostriction increases at low temperatures. The electromechanical strain has a structural nature and can rise by one order of magnitude, i.e., from 5 × 10-4 at room temperature to 5 × 10-3 at -193 °C, due to an increase in the population of the electrically active pairs. At a constant VO concentration, the material can thus configure heterogeneous pairs and elastic nanodomains that are either mechanically responsive or not.
缺氧氧化铈，例如钆掺杂氧化铈，表现出与其晶格复杂的局部重排相关的巨大机电性能。尽管尚未完全确定，但电活性机制源于阳离子和氧空位（VO）对（即Ce-VO）及其周围的局部结构弹性畸变。在此，我们研究了在约11 kV cm-1的交流电场下，无晶界块状Ce0.9Gd0.1O1.95单晶中Ce-VO对的几何结构和行为。通过Ce L-III边缘的X射线吸收光谱（XAS）技术进行分析。使用密度泛函理论（DFT）计算，我们研究了应变对价带边缘态密度和轨道的影响。我们的研究表明，电致伸缩在低温下会增加。机电应变具有结构性质，并且由于电活性对数量的增加，其可以增加一个数量级，即从室温下的5×10-4增加到-193°C时的5×10-3。因此，在恒定的VO浓度下，该材料可以配置出对机械响应或不响应的异质对和弹性纳米域。
