Synthesis, Structure, and Physical Properties of A-site Ordered Perovskites ACu3Co4O12 (A = Ca and Y)
Synthesis, Structure, and Physical Properties of A-site Ordered Perovskites ACu3Co4O12 (A = Ca and Y)
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DOI：
10.1021/cm101671j
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发表时间：
2010-08
影响因子：
8.6
通讯作者：
I. Yamada;S. Ishiwata;I. Terasaki;M. Azuma;Y. Shimakawa;M. Takano
中科院分区：
文献类型：
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作者：
I. Yamada;S. Ishiwata;I. Terasaki;M. Azuma;Y. Shimakawa;M. Takano
在高压(9 Gpa)和高温(1273K)下合成了A位有序钙钛矿CaCu3Co4O12和YCu3Co4O12及其固溶体Ca1−xYxCu3Co4O12(x=0.2 5，0.5 0和0.75)。它们都具有CaCu3Ti4O12型结构(立方，空间群：IM3)，晶格常数a从CaCu3Co4O12的7.1226(5)A略微降低到YCu3Co4O12的7.1195(3)A。基于同步辐射粉末X射线衍射的Rietveld精修表明，CaCu3Co4O12的价态接近于CaCu3+3Co3.25+4O12，这与其他钙钛矿的价态不同。在A位用Y取代Ca使金属CaCu3Co4O12转变为绝缘的YCu3Co4O12，金属−绝缘体在x=0.50−0.75时发生转变。电阻率、热电性和比热结果表明，电子被掺杂到Co3d带中，价态从CaCu3+3Co3.25+4O12转变为YCu3+3Co3+4O12。
A-site ordered perovskites CaCu3Co4O12 and YCu3Co4O12, and their solid solutions Ca1−xYxCu3Co4O12 (x = 0.25, 0.50, and 0.75), were synthesized under high pressure (9 GPa) and high temperature (1273 K). They all have a CaCu3Ti4O12-type structure (cubic, space group: Im3) and the lattice constant a slightly decreased from 7.1226(5) A of CaCu3Co4O12 to 7.1195(3) A of YCu3Co4O12. Rietveld refinement based on synchrotron powder X-ray diffraction suggests that the valence state of CaCu3Co4O12 is close to CaCu3+3Co3.25+4O12, which differs from those of other CaCu2+3B4+4O12 perovskites. Substitution of Ca with Y at the A-site changes the metallic CaCu3Co4O12 to an insulating YCu3Co4O12, and a metal−insulator transition occurs at x = 0.50−0.75. The electrical resistivity, thermoelectricity, and specific heat results reveal that electrons are doped into the Co 3d band and that the valence state changes from CaCu3+3Co3.25+4O12 to YCu3+3Co3+4O12.