Heat Treatment of Nd_(1+x)Ba_(2-x)Cu_3O_(7-δ) Superconductors

摘要

Two kinds of Nd_(1+x)Ba_(2-x)Cu_3O_(7-δ), the sintered samples and zone melted samples, were treated in pure Ar at 950℃. The substitution of Nd ions for Ba ions in the Nd_(1+x)Ba_(2-x)Cu_3O_(7-δ) before and after the heat treatment was investigated by XRD. In order to know the effects of heat treatment, the T_c and J_c of samples with and without the heat treatment in Ar were comparatively studied. The results show that the substitution of Nd for Ba decreases, whereas T_c and J_c increase after the treatment. The Nd_(1+x)Ba_(2-x)Cu_3O_(7-δ) samples were oxygenated in pure oxygen at 300℃. Based on the XRD spectra it was found that the samples with x < 0.4 can transform from tetragonal phase into orthorhombic phase after the oxygenation, whereas in the sample with x > 0.4 no phase transition occurs even after a long time oxygenation.