| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2003: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2002: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
New materials showing superconductivity at high temperatures have been earnestly desired. They are useful as materials of the wire of the MRI magnet. We have made fundamental researches on synthesis of new superconducting oxides being agreeable to the materials. We show summary of the research results below.
We had searched new materials belonging to the Ru-based oxide superconductors, because of their useful nature showing high-T_c superconductivity without such any treatment for hole-doping as annealing under high-pressure O_2 atmosphere. As a result, we succeeded for the first time in synthesis of the 1232 phase showing superconductivity and ferromagnetism in the Ru-Sr-Ln(Ce)-Cu-O system (Ln=Sm, Eu and Gd). Interestingly, he T_c values are increasing as the lattice parameters are becoming small, and the value comes to the maximum one in the case of the sample with Ln=Gd. This result can be expected that the T_c values correlate the lattice parameters. From this expectation, we perfor
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med an experiment of partial substitution of Nb for Ru in the Ru-based 1232 sample with Ln=Gd. Ionic radius of Nb is bigger than that of Ru. Then, we obtained such an experimental result that with increasing of the substituted quantity of Nb, the lattice parameters were increasing, the T_c values were expectedly decreasing. Then, we prepared many samples partially substituted for Gd by Sm, Dy and Ho. As a result, we discovered that the T_c values were increasing, when Dy or Ho with smaller ionic radius were selected for a substituted element. This is one of important experimental facts obtained by us, it suggests that the stress due to the mismatches between the perovskite-type blocks containing the CuO_2 pyramids and the fluorite-type ones existing in the crystal structure affects on the T_c values.
Moreover, we have also succeeded in synthesizing new Bi-based superconductor of the 2212 phase by partial substitution of Pb for Sr and/or Bi in the Bi-Sr-La-Cu-O system. The Bi-2212 compound has never been synthesized in the Bi-Sr-La-Cu-O system because of similar values of the ionic radii of Bi^<3+>, Sr^<2+> and La^<3+>. This is also one of important experimental results obtained by us, it shows that our supposed materials can be realized by controlling the ionic radius of the constituent elements. Less
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