Malavasi Lorenzo, Kim Hyunjeong, Billinge Simon J L, Proffen Thomas, Tealdi Cristina, Flor Giorgio
Department of Physical Chemistry and IENI/CNR Department of Pavia University of Pavia, Pavia, 27100 Italy.
J Am Chem Soc. 2007 May 30;129(21):6903-7. doi: 10.1021/ja071281e. Epub 2007 May 8.
La2Mo2O9 (LAMOX) is a fast oxygen ion conductor which shows high oxygen ion conductivities comparable to those of yttria-sabilized zirconia (YSZ). LAMOX is subject to a structural phase transition from the nonconductive monoclinic form to the highly conductive cubic form at about 580 degrees C. The origin of the conductivity in cubic LAMOX has been suggested to be due to a "disorder" in the O sublattice without any insight into the real distribution of the oxygen ion. In this paper, thanks to the application of the neutron atomic pair distribution function (PDF) analysis, we provide evidence that the local structure of the cubic polymorph of LAMOX is exactly the same of that of the monoclinic phase, thus indicating that the structural phase transition is actually a transition from a static to a dynamic distribution of the oxygen defects. This work represents the first application of the atomic-pair distribution function analysis to the study of an oxygen fast-oxide ion conductor and clearly indicates that a more reliable and detailed description of their local structure, particularly in the highly conductive phases, can lead to a better comprehension of the structure-property correlation, which is the starting point for the design of new and optimized functional materials.
La2Mo2O9（LAMOX）是一种快速氧离子导体，其氧离子电导率很高，可与钇稳定氧化锆（YSZ）相媲美。LAMOX在约580摄氏度时会发生结构相变，从非导电的单斜晶相转变为高导电的立方晶相。立方相LAMOX导电率的来源被认为是由于氧亚晶格中的“无序”，但对氧离子的实际分布并无深入了解。在本文中，由于应用了中子原子对分布函数（PDF）分析，我们提供了证据表明LAMOX立方多晶型的局部结构与单斜晶相完全相同，这表明结构相变实际上是氧缺陷从静态分布到动态分布的转变。这项工作代表了原子对分布函数分析首次应用于氧快速氧化物离子导体的研究，并清楚地表明对其局部结构进行更可靠、更详细的描述，特别是在高导电相中，可以更好地理解结构-性能关系，这是设计新型优化功能材料的起点。
