Gd <sub> 2 </ Sub> The O <sub> 3 </ Sub> Doping Of Cu <sub> Gdba <sub> 2 </ Sub> </ Sub> O <sub> 7-¦Ä </ Sub > The Impact Of The Superconducting Crystal Growth

High Tc Y-Based superconducting material is one of the most useful high temperconductors. The GdBa₂Cu₃O_7-δ bulk superconductors have significant potential for practical engineering applications, such as maglev, magnetic bearings, permanent magnets, flywheel energy storage systems and superconducting motors, since they have high critical temperature(Tc), high critical current density(Jc) and strong trapped magnetic fields. The preparation, microstructure and levitation force of GdBa₂Cu₃O_7-δ bulk superconductor have been studied in this paper.The GdBa₂Cu₃O_7-δ single domain bulks have been fabricated by top seeded melt textured growth(TSMTG) process. The GdBa₂Cu₃O_7-δ single domain bulks, with diameters ofφ18mm orφ28mm have been fabricated by TSMTG process, the microstructure and levitation force of the GdBa₂Cu₃O_7-δ bulk superconductors have also been studied in this paper.GdBa₂Cu₃O_7-δ powders were synthesized by the solid state reaction method, and it was sinterd at 940℃for several times with an interval of milling.Jc is strongly dependent on microstructure of GdBa₂Cu₃O_7-δ bulk superconductor, and the addition of Gd₂BaCuO₅ particles to GdBa₂Cu₃O_7-δ precursor pellets can prevent the melt loss during the melting temperature stage and act as flux pinning centers in the sample. The superconducting properties of GdBa₂Cu₃O_7-δ may be improved by using Gd₂O₃ instead for Gd₂BaCuO₅ addition, which could be capable to reduce the cost on the fabrication of GdBa₂Cu₃O_7-δ bulk supercondors.In order to depress the random nucleation during the preparation of single domain GdBa₂Cu₃O_7-δ bulk superconductors, YBa₂Cu₃O_7-δ material with lower melting temperature (compared with GdBa₂Cu₃O_7-δ is used to realize this goal. The YBa₂Cu₃O_7-δ material was just added to the bottom of the GdBa₂Cu₃O_7-δ bulks in a thin layer. The YBa₂Cu₃O_7-δ layer is able to depress the random nucleation from the bottom of the sample during the preparation process.Single domain GdBa₂Cu₃O_7-δ bulk superconductors((p20mm), with differert additions of Gd₂O₃, have been fabricated by TSMTG process, the content of Gd₂O₃ is in the rang of 4wt% to 10wt%. The levitation force of single-domain GdBa₂Cu₃O_7-δ bulk have been measured at liquid nitrogen temperature under zero field cooling condition. It is found that the maximum levitation force of the samples is of a peak value while the Gd₂O₃ addition increases from 4wt% to 10wt%. The maximun magnetic levitation force is about 6N, corresponding to the sample with 7.5wt% Gd₂O₃ addition.The influences of magnetic field distribution of permanent magnet on the levitation force ofGdBa₂Cu₃O_7-δ bulk superconductor have been investigated under the Zero Field Cooled (ZFC) condition. The sample is a GdBa₂Cu₃O_7-δ bulk superconductor with the diameter ofφ28mm prepared by TSMTG process. The permanent magnet used in this study is ofφ10mm,φ20mm,φ25mm,φ40mm andφ50mm in diameter respectively, the maximum magnetic flux density at the tope surface is about 0.5T. It is found that the levitation force of the GdBa₂Cu₃O_7-δ bulk superconductor increases at first and then decreases with the increasing of the permanent magnet diameter. The largest force can be abtained when the size of the permanent magnet approaches to that of the GdBa₂Cu₃O_7-δ bulk superconductors.