1996 Fiscal Year Final Research Report Summary
Studies of Metal-Insulator Transition and Investigations and Materials with Infinite-layr Structure
| Project/Area Number |
07650783
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | Nagoya University |
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Principal Investigator |
OHMORI Kazuhiko School of Engineering, Nagoya University Research Associate, 工学部, 助手 (30023188)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUI Masaaki School of Engineering, Nagoya University Professor, 工学部, 教授 (90013531)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Infinite-layr structure / Body center site / SrCuO_2-type / Ca_2CuO_3-type / High pressure synthesis / Electric resistivity / Superconductivity / average ionic radius |
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| Research Abstract |
Materials with infinite-layr structure is expressed by chemical formula ACuO_2 where A is an atom at body-center site and placed between CuO_2-Planes. This material has a 2D structure made of alternately stacked A and [CuO_2]_* layrs. Material of A=Sr_<0.14>Ca_<0.86> which was prepared by solid phase reaction under ambient pressure has the infinite-layr structure and its conductivity is not superconductive. We made composite atom by addition or substitution of another atom with different ionic radius and valence and investigated superconductor with the infinite-layr structure which could be prepared under ambient pressure. Cases of A=Sr_<1-x>Ca_x had the infinite-layr structure in X=0.83-0.90, SrCuO_2-type structure in X=0-0.65 and Ca_2CuO_3-type structure in X=0.98-1.0. A=Sr_<1-x>Bi_x(X=0.15,0.3) systems had Cu_2SrO_3 type in majority, and Bi_2Sr_2CuO_y(2201 phase) appeared in X=0.5 system. A=Sr_<1-x>Pb_x system had three phase. A=(Ca_<0.86>Sr_<0.14>)_<1-x>Li_x system has Ca_2CuO_3-ty
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pe in majority. A=(Ca_<0.86>Sr_<0.14>)_<1-x>K_x system had the infinite-layr structure in X=0.1,0.2. In cases of X=0.3-0.5, the infinite-layr structure appeared when samples were treated in temperature near to melting point. Results of EDX composition analysis meant evapolation or sublimation of K atom from samples. A=(Ca_<0.86>Sr_<0.14>)_<1-x>Na_x system had Ca_2CuO_3-type and SrCuO_2-type structure, and A=(Ca_<0.86>Sr_<0.14>)_<1-x>Rb_x had Ca_2CuO_3-type. The infinite-layr structure disappeared in A=(Ca_<0.86>Sr_<0.14>)_<1-x>R_x(R=La, Ce, Pr, Nd). Electric resistivity were semi-conductive in most of the samples.
While A=Sr_<0.7>Ca_<0.3> had the SrCuO_2-type structure under ambient pressure as mentioned above, high pressure synthesis of A=(Sr_<0.7>Ca_<0.3>)_<0.9> resulted in crystallization of the infinite structure and showed superconductivity. Transition temperature of sample heated at 950ﾟC is 110K (onset) in electric resistivity and that of sample heated at 1100ﾟC is 118K in magnetic measurement. Crystal structure of samples were classified by ratio of average ionic radius of cation except Cu to ionic radius of anion (0^<-2>) but A=Sr_<1-x>Ca_x(X=0-0.65) and A=(Ca_<0.86>Sr_<0.14>)_<1-x>Rb_x(X=0.05,0.1) samples. Less
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Research Products
(4 results)
