PREPARATION AND CRYSTAL-STRUCTURE OF THE DEFICIENT PEROVSKITE LANIO2.5, SOLVED FROM NEUTRON POWDER DIFFRACTION DATA
PREPARATION AND CRYSTAL-STRUCTURE OF THE DEFICIENT PEROVSKITE LANIO2.5, SOLVED FROM NEUTRON POWDER DIFFRACTION DATA
复制标题
DOI：
10.1039/dt9950002819
复制
发表时间：
1995-09-07
期刊：
影响因子：
--
通讯作者：
MARTINEZLOPE, MJ
中科院分区：
文献类型：
--
作者：
ALONSO, JA;MARTINEZLOPE, MJ
通过在400 ℃的真空安瓿中用Zr金属对LaNiO 3进行受控还原，以粉末形式制备了具有优异结晶度的缺陷型钙钛矿LaNiO2.5。中子粉末衍射图可以在对应于尺寸为2a（0）x 2a（0）x 2a（0）（a（0）：理想立方钙钛矿的晶格参数）的钙钛矿超结构的单斜晶胞中索引，也通过电子衍射观察到。结构是从中子粉末数据中解出的。氧空位以这样的方式排列，即正方形平面NiO 4和NiO 6八面体在ab平面中沿着[110]方向交替：为了优化La-O距离，两种Ni多面体都相当扭曲和倾斜。产生亚稳特性的高度应变结构事实上，该化合物容易吸收氧。高于175摄氏度的空气中，以得到更稳定的LaNiO 3钙钛矿。
The deficient perovskite LaNiO2.5 has been prepared in powder form with excellent crystallinity by controlled reduction of LaNiO3 with Zr metal in evacuated ampoules at 400 degrees C. The neutron powder diffraction pattern could be indexed in a monoclinic unit-cell corresponding to a superstructure of perovskite with dimensions 2a(0) x 2a(0) x 2a(0) (a(0): lattice parameter of the ideal cubic perovskite), also observed by electron diffraction. The structure was solved from the neutron powder data. The oxygen vacancies are ordered in such a way that square-planar NiO4 and NiO6 octahedra alternate in the ab plane along the [110] direction: Both kinds of Ni polyhedra are fairly distorted and tilted in order to optimize the La-O distances. giving rise to a highly strained structure of metastable character In fact, the compound: readily takes up oxygen. above 175 degrees C in air, to give the much more stable LaNiO3 perovskite.