SOLID IONIC PROPERTIES OF METASTABLE ZrO_2-CeO_2-CeO_<1.5> SOLID SOLUTIONS

在金属-氧体系中，单一相的还原和连续氧化可以制备各种亚稳相；氧化过程保持了还原相前驱体中阳离子的分布。将这一原理应用于ZrO_2-CeO_2系统，表征了得到的贵金属亚稳相的局域原子位移和固体离子性质。通过在T_&lt；de&gt；=873K-1573K处还原t‘-(Ge_&lt；0.5&gt；Zr_&lt；0.5&gt；O_2)相制备了前驱体。当T_&lt；de&gt；=1573K在873K被氧化时，得到了具有有序排列的贵金属亚稳相-CeSiO_4 pHa。前驱体用1173K氧化生成了另一种贵金属亚稳相t‘&lt；meta&gt；-(Ce_&lt；0.5&gt；Z_&lt；0.5&gt；O_2)，其中Ce和Zr的无序排列类似于t’-(Ce_&lt；0.5&gt；0.5&gt；O_2)。Ce-O-Ce离子之间的距离按t‘*t’&lt；meta&gt；*kappa.的顺序递减，尽管组成相同：CeZrO4，但亚稳态的t‘&lt；meta&gt；和kappa相的电导率远大于t’.结果可以用Ce-O-Ce距离、阳离子分布和氧位移量来解释。研究结果表明，通过亚稳相的制备和杂质的掺杂可以控制薄膜的电学性能。

In the metal-oxygen system, reduction and successive oxidation of a single phase make possible to prepare various metastable phases ; the oxidation proceeds remaining the cation distribution in the precursor of reduced phase. This principle was applied to ZrO_2 - CeO_2 system, the local atom displacements and solid ionics properties of the noble metastable phases obtained were characterizedThe precursors were prepared by reducing the t'-(Ge_<0.5>Zr_<0.5>O_2) phase at T_<de>=873K-1573K.When the precursor with T_<de>=1573K was oxidized at 873 K, a noble metastable kappa-CeZiO_4 phas was obtained in which Ce and Zr are in an ordered arrangement. The oxidation of the precursor with 1173K produced another noble metastable t'_<meta>, -(Ce_<0.5>Z_<0.5>O_2) phase in which Ce and Zr are in an disordered arrangement similar to t'-(Ce_<0.5>, Zr_<0.5>O_2). The distance between Ce-O-Ce ions decreased in the order of t'* t'_<meta> * kappa.In spite of the same composition : CeZrO_4, the electrical conductivity of the metastable t'_<meta> and kappa phases were found to be fairly larger than that of t'. The results couled be interpreted in terms of the Ce-O-Ce distance, cation distribution, and oxygen displacement. The present results imply that the electrical properties could be controlled by the preparation of metastable phase as well as doping of impurities.