The influence of next nearest neighbours on cation radii in spinels: the example of the Co3O4–CoCr2O4 solid solution
The influence of next nearest neighbours on cation radii in spinels: the example of the Co3O4–CoCr2O4 solid solution
复制标题
尖晶石中次近邻对阳离子半径的影响：以 Co3O4-CoCr2O4 固溶体为例
DOI：
10.1180/0026461036730116
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发表时间：
2003
影响因子：
2.7
通讯作者：
H. O’Neill
中科院分区：
文献类型：
--
作者：
H. O’Neill
用X射线粉末衍射法测定了合成尖晶石Co_3O_4、CoCr_2O_4和Co_3O_4-CoCr_2O_4二元固溶体的晶格参数和晶体结构。在所有这些尖晶石的阳离子分布是完全正常的，在室温下，和四面体配位的阳离子位点被占领的Co 2+。Co ~（2+）的离子半径（泰特）从Co_3O_4的0.556（3）增加到CoCr_2O_4的0.599（4）。在尖晶石结构中，四面体阳离子和氧之间的原子间距离在几何上独立于八面体阳离子和氧之间的原子间距离;因此，有效离子半径的变化归因于次近邻效应，由低自旋Co 3 +-O键中的共价趋势引起。结果表明，即使在氧化物尖晶石等同晶群中，离子半径恒定的假设也需要谨慎。
Abstract Lattice parameters and crystal structures of the synthetic spinels Co3O4, CoCr2O4, and solid solutions in the binary join Co3O4-CoCr2O4, have been determined by powder X-ray diffraction structural refinements. In all these spinels the cation distribution is completely normal at room temperature, and the tetrahedrally coordinated cation site is occupied only by Co2+. The ionic radius of Co2+(tet) increases from 0.556(3) in Co3O4 to 0.599(4) in CoCr2O4. In the spinel structure, the interatomic distance between the tetrahedral cations and oxygen are geometrically independent of those between the octahedral cations and oxygen; thus the variation in effective ionic radii is ascribed to next-nearest neighbour effects, induced by covalent tendencies in the low-spin Co3+-O bond. The results demonstrate that the assumption of constant ionic radii even within an isomorphic group such as the oxide spinels needs to be made with caution.