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，氧化过程保持还原相前体中的阳离子分布。将这一原理应用于ZrO_2 - CeO_2系统，对所得到的贵金属亚稳相的局域原子位移和固体离子学性质进行了表征。在873 K-1573 K温度范围内还原t '-（Ge_<0.5>Zr_<0.5>O_2）相<de>制备了前驱体，<de>在873 K温度下氧化1573 K的前驱体，得到了Ce和Zr有序排列的贵金属亚稳kappa-CeZiO_4相。在1173 K下氧化生成了另一种贵金属亚稳相t '<meta>-（Ce_，<0.5>Zr_<0.5>O_2），其中Ce和Zr以类似于t'-（Ce_<0.5>，Zr_<0.5>O_2）的无序排列。Ce-O-Ce离子间的距离按t ′ * t ′_* kappa的顺序减小<meta>，即使在相同的CeZrO_4组成下，介稳相的电导率也<meta>比t ′大得多。结果可以从Ce-O-Ce距离、阳离子分布和氧置换等方面进行解释。这些结果表明，通过制备亚稳相和掺杂杂质可以控制其电性能。

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.