Zamudio-García Javier, Porras-Vázquez Jose M, Cabeza Aurelio, Canales-Vázquez Jesús, Losilla Enrique R, Marrero-López David
Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs. Lyngby, Denmark.
Dpto. de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071 Málaga, Spain.
ACS Appl Mater Interfaces. 2024 Aug 14;16(32):42198-42209. doi: 10.1021/acsami.4c07437. Epub 2024 Aug 1.
Rare-earth doped CeO materials find extensive application in high-temperature energy conversion devices such as solid oxide fuel cells and electrolyzers. However, understanding the complex relationship between structural and electrical properties, particularly concerning rare-earth ionic size and content, remains a subject of ongoing debate, with conflicting published results. In this study, we have conducted comprehensive long-range and local order structural characterization of CeLnO samples ( ≤ 0.6; Ln = La, Nd, Sm, Gd, and Yb) using X-ray and neutron powder diffraction, Raman spectroscopy, and electron diffraction. The increase in the rare-earth dopant content leads to a progressive phase transformation from a disordered fluorite structure to a C-type ordered superstructure, accompanied by reduced ionic conductivity. Samples with low dopant content ( = 0.2) exhibit higher ionic conductivity in Gd and Sm series due to lower lattice cell distortion. Conversely, highly doped samples ( = 0.6) exhibit superior conductivity for larger rare-earth dopant cations. Thermogravimetric analysis confirms increased water uptake and proton conductivity with increasing dopant concentration, while the electronic conductivity remains relatively unaffected, resulting in reduced ionic transport numbers. These findings offer insights into the relationship between transport properties and defect-induced local distortions in rare-earth doped CeO, suggesting the potential for developing new functional materials with mixed ionic oxide, proton, and electronic conductivity for high-temperature energy systems.
稀土掺杂的CeO材料在高温能量转换装置中有着广泛应用，如固体氧化物燃料电池和电解槽。然而，理解结构与电学性质之间的复杂关系，尤其是关于稀土离子尺寸和含量的关系，仍然是一个持续争论的话题，已发表的结果相互矛盾。在本研究中，我们使用X射线和中子粉末衍射、拉曼光谱以及电子衍射对CeLnO样品（≤0.6；Ln = La、Nd、Sm、Gd和Yb）进行了全面的长程和局域有序结构表征。稀土掺杂剂含量的增加导致从无序萤石结构到C型有序超结构的逐步相变，同时离子电导率降低。低掺杂含量（= 0.2）的样品在Gd和Sm系列中由于较低的晶格畸变而表现出较高的离子电导率。相反，高掺杂样品（= 0.6）对于较大的稀土掺杂阳离子表现出优异的电导率。热重分析证实随着掺杂剂浓度增加吸水量和质子电导率增加，而电子电导率相对不受影响，导致离子传输数降低。这些发现为稀土掺杂CeO中传输性质与缺陷诱导的局域畸变之间的关系提供了见解，表明开发具有混合离子氧化物、质子和电子电导率的新型功能材料用于高温能量系统的潜力。
