Effect of SnO2 and CeO2 doping on the microstructure and superconducting properties of melt textured zone YBa2Cu3O7-δ

The microwave melt textured growth process (MMTG) is used to investigate the influence of CeO2 and SnO2 doping and their combination with two different Sn/Ce initial ratios on the YBa2Cu3O7-δ (Y123) growth mechanism, microstructure and superconducting properties. It was shown that the combination of 'CeO2 + SnO2' allows us to increase the Y123 crystal growth velocity compared with CeO2 used alone. Furthermore, this combination reduces the Y2BaCuO5 particle coarsening observed when SnO2 doping is added alone. Secondary phase SEM observations show that square submicrometric precipitates are homogeneously distributed in the matrix when 'CeO2 + SnO2' are used. Thus, the identified phase appears to be a solid solution derived from the phase Ba2YSnO5.5 : Ba2(Y2/3-xCux)(Ce, Sn)4/3O6-δ. In this article, the initial Sn/Ce ratio was found to be a crucial parameter that affects the matrix purity. In terms of superconducting properties, 'CeO2 + SnO2' doped samples exhibit the highest magnetic critical current density in zero field (55 kA cm-2), even under 1 Tesla (25 kA cm-2), depending on the Sn/Ce ratio. The superconducting properties are discussed in relation with the microstructure and the EDS analysis results. (author)