YBa2Cu3Oyの超電導性におよぼすY-La置換の影響

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Effects of La addition substituting for Y in YBa2Cu3Oy on the supercoductivity were investigated. Powder mixtures of Y2O3, BaCO3, La2(CO3)3 and CuO were prepared by mechanical method, cold pressed at the pressure of 98 MPa, sintered at 1253K for 86.4 ks followed by 523K for 86.4ks and then furnace cooled in an oxygen atmosphere. For estimating the superconductivity, electrical resistivity versus temperature was measured. X-ray diffraction analysis was performed to obtain diffraction patterns and determine lattice constants by using graphite monocromatized CuKα radiation and diffractometer. Substitution of La for Y in YBa2Cu3Oy did not influence on Tc up to approximately 0.1mol La of Y in YBa2Cu3Oy. However, ΔTc was minimal at approximately 0.1mol La of Y, that is, superconductivity was stabilized by the substitution of La for Y. Over this, Tc inclined to lower with increasing La content. These experimental results may be related to the fact that sintered density of Y0.9La0.1Ba2Cu3Oy became larger than that of YBa2Cu3Oy at the same sintering conditions. Tcoffset was achieved at 84 K for La0.64Ba2Cu3Oy sample; this is the highest Tc obtained among the LaBaCuO ceramics reported so far. Lattice parameters of orthorhombic Y1-xLaxBa2Cu3Oy increased monotonously with the increase of La content up to 1 mol La of Y. Orthorhombic single phase was kept to exist up to approximately 0.2 mol of La for Y. Over this, mixture of orthorhombic phase and other phases were confirmed to be coexistent in the specimens.

YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>y</SUB>の超電導性におよぼすY-La置換の影響

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