Nd1+XBa2-XCu3O7-δBulk Superconductor by Zone-melt Process

Abstract

Two kinds of <TEX>$Nd_{1+X}Ba_{2-X}Cu_3O_{7-{\delta}}$</TEX>, the sintering samples and zone melting samples, were heat-treated under pure Ar at 950<TEX>$^{circ}C$</TEX>. The substitution of Nd ion for Ba ion in the <TEX>$Nd_{1+X}Ba_{2-X}Cu_3O_{7-{\delta}}$</TEX> before and after the heat treatment was investigated by XRD. In order to confirm the effects of the heat treatment, the Tc and Jc of samples with/without the heat treatment under Ar were comparatively studied. <TEX>$Nd_{1+X}Ba_{2-X}Cu_3O_{7-{\delta}}$</TEX> samples were oxygenated under pure oxygen at <TEX>$300^{circ}C$</TEX>. From the XRD pattern it was found that the sample with x<0.4 was transferred from tetragonal phase to orthorhombic phase after the oxygenation, while the sample with x>0.4 did not show the phase transition even after a long time oxygenation. Therefore, the low oxygen partial pressure (Ar+1 % O<TEX>$_2$</TEX>) was used for the ambient atmosphere of the zone-melting samples, which could reduce the melting temperature and depress the substitution of Nd for Ba. After the improvement in the zone-melting process, the Jc value was increased to 2 x <TEX>$10^4$</TEX>A/<TEX>$cm^2$</TEX> (0 T, 78 K). The particle orientation and the structure of zone-melted NdBaCuO were studied by the XRD and SEM analysis.