YBa2Cu3O7-δ酸化物の超電導性におよぼすLa添加の影響

概要

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Effects of La addition substituting for Ba in YBa2Cu3O7-d on the superconductivity were investigated. Powder mixtures of Y2O3, BaCO3 (La(CO3)3) and CuO were prepared by mechanical method, cold pressed at the pressure of 98MP, sintered at 1173-1253K for 86.4 -172.8 ks and then furnace cooled in an oxygen atmosphere. For estimating the superconductivity, electrical resistivity versus temperature was measured. X-ray powder diffraction patterns were obtained by using CuK α radiation and diffractometer. Substitution of La for Ba in YBa2Cu3O7-d resulted to lower the Tc; at about 10% La substitution for Ba, Tc dropped below 77K. ΔTc had a tendency to broaden with increasing La content. Lattice parameters of orthorombic type were changed from a = 3.884(0)(A), b =3.819(7)(Å), c =11.670(3)(Å) for YBa2Cu3O7-d to a =3.886(6)(Å), b = 3.816(8)(Å), c =11.655(9)(Å) for YBa1⋅9La0⋅1Cu7-r (L/Ba=5mass%).