The Effect Of BaCeO₃ Particles Doping On Microstructure And Superconducting Properties Of YBa₂Cu₃O_7-δ+Y₂O₃

Since 1911, Dutch scientist Onnes discover superconductors, people have made a lot of research about superconductors, has found that different kinds of superconducting materials.YBa₂Cu₃O_7-δ（Y123,YBCO） is one of the most studied in the high temperature superconducting materials, the most widely used material.The people mainly for YBCO critical transition temperature and critical current density and critical magnetic field is studied, the commonly used method is to doping YBCO high temperature superconductor materials, doping mainly include element substitution and the introduction of the second phase particles.The study found that doping of YBCO superconducting properties have great influence, which can realize some applications in the life. So this article main research content is Y₂O₃ and BaCeO₃ powder for polycrystalline YBCO superconductor and the effect of the microstructure and superconductivity.The BaCeO₃ powder is prepared by sol gel, and the polycrystalline YBCO superconductor materials was fabricated via solid-state reaction, then the Y₂O₃ and Ba CeO3 powder doped into the YBCO superconducting materials according to the different proportion, prepared a series of superconducting material by solid phase method. At the same time, the series of superconductor lattice structure,microstructure and element distribution and critical transition temperature is system characterized and analyzed.1. Different levels of BaCeO₃ + 0.25 mol Y₂O₃ powders doping YBCO superconducting properties study shows: The Y₂O₃ was added to the YBCO, the samples have many Y211 formations and look like spherical or ellipsoidal shape.According to SEM, XRD and resistivity measurements, we observe that with increased of BaCeO₃ concentration, the morphology becomes more and more inhomogeneous, all samples change the structure from orthorhombic to tetragonal and the normal state resistivity shows a change from metallic to semi-conducting behavior,and the samples of transition temperature appear to three steps transition, Meantime,the temperature of the samples transition significantly decreases and transition widthobviously broadens.These results can be interpreted by impurity introduced and by the variation of defects, and oxygen decadency.2. Different levels of BaCeO₃ + 0.25 mol Y₂O₃ powders doping YBCO superconducting properties study shows: The Y₂O₃ was added to the YBCO, the samples have a little of Y211 formations and look like spherical or ellipsoidal shape.According to SEM, XRD, EDS and resistivity measurements, we observe that the Ba CeO3 doping concentration reached to 5%, the morphology of those samples exhibits a granular structure and has big gap among particles, and becomes inhomogeneous, but Y and O distribution basic remain unchanged.When the BaCeO₃ doping concentration > 1%, the samples normal state resistivity shows a change from metallic to semi-conducting behavior, and the temperature of the samples transition slightly decreases and transition width slightly broadens. These results can be interpreted by the increase of oxygen content and by impurity introduced, and intra-grain disorders and weak-link. Drawing conclusion from experiment that different performance was optimum when doping amount of BaCeO₃ was 1.0%.