Valence and Coordination State Analysis for Transition Metal Ions Mixed Conductive Perovskite Oxides

过渡金属离子混合导电钙钛矿氧化物的价态和配位态分析

基本信息

批准号：
06650779
负责人：
YAO Takeshi
金额：
$ 1.34万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06650779/
关键词：
Perovskite structure Crystal structure analysis Rietveld method Mangenese ion Jahn-Teller effect Cobalt ion Electrical conductivity Valence バンド構造金属-絶縁体転移

项目摘要

Rare earth containing perovskite oxides with mixed conductive properties in which both ions and electrons move as charge carriers were heat-treated under various oxygen partial pressures and temperatures for various kinds of alkaline earth compositions. The crystal structures were precisely analyzed by powder X-ray Rietveld analysis. Then the relations between the changes in valence and coordination states of the transition metal ions and the properties such as electrical conductivity etc.were investigated. La : Mn=1 : 1, La substituted La-Sr-Mn-O or Mn substitute La-Mn-Mg-O perovskite oxides were heat-treated under various oxygen partial pressures. The Mn valence of the samples were measured by a chemical analysis, and the crystal structure were refined by the powder X-ray diffraction and the Rietveld analysis. A novel orthor-hombic perovskite phase containing Mn^<2+> ions was formed by heat-treatment under low oxygen partial pressures. The structure was very close to a cubic symmetry. It is supposed that the micro Jahn-Teller effects of Mn^<2+> ions were nearly canceled by one another. Crystal structure of perovskite La_<1-x>Sr_xCoO_3 was precisely determined by powder X-ray Rietveld analysis, the mean valence of cobalt ion was measured by iodometry, and the correlation with the electrical property was investigated. The valence of the cobalt ion showed a stoichiometric change for the lower amount of Sr, however, the deviation from the stoichiometry increased with the increase of Sr. With the increase of Sr amount, there observed an abrupt decrease for CoO distance by the Rietveld analysis, and the transition from semiconducting to metallic in the electrical conductivity. It is considered that the charge transfer gap existing between O-2p band and Co-d band was closed by the change in the crystal structure.

稀有地球含有具有混合导电性能的钙钛矿氧化物，其中离子和电子在各种氧气部分压力和温度下对各种碱性土组成进行了热处理。通过粉末X射线rietveld分析精确分析晶体结构。然后研究了过渡金属离子的价变化和配位状态与电导率等性能之间的关系。 LA：MN = 1：1，LA取代的LA-SR-MN-O或MN替代替代La-Mn-Mg-O钙钛矿氧化物在各种氧气压力下进行热处理。通过化学分析测量样品的MN价，并通过粉末X射线衍射和Rietveld分析来完善晶体结构。在低氧部分压力下进行热处理形成了一种新型的含Mn^<2+>离子的新型植物钙钛矿相。该结构非常接近立方对称性。据认为，Mn^<2+>离子的微jahn-teller效应几乎彼此取消。 Perovskite la_ <1-X> SR_XCOO_3的晶体结构由粉末X射线rietveld分析精确确定，通过碘法测量了钴离子的平均价，并研究了与电性能的相关性。钴离子的价显示较低的SR的化学计量变化，但是，随着SR的增加，与化学计量的偏差随着SR的增加而增加，观察到Rietveld分析的COO距离突然降低，并且从半传导到电子电导率的过渡。据认为，晶体结构的变化封闭了O-2P频段和Co-D波段之间存在的电荷传递差距。