Influence of different melt processings upon the microstructure and critical current of textured Y123

• Published in: Physica. C, Superconductivity Superconductivity, 1996-08, Vol.267 (1), p.173-182
• Main Authors: Monot, I., Wang, J., Delamare, M.P., Provost, J., Desgardin, G.
• Format: Article
• Language: English
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/0921-4534(96)00345-0

Since directional solidification has been shown to be a successful way for achieving high critical current densities in bulk YBCO, many different ways have been developed for the sample preparation. In this study, the microstructure and superconducting properties of several processing routes (melt powder melt growth, powder melt processing, solid liquid melt growth) have been comparatively investigated. These processings are distinguished essentially from the combination of different starting precursors. It is shown that Y 2BaCuO 5 (Y211) excess in the nominal composition and/or 0.5 wt.% platinum doping strongly influence the shape of the Y211 formed during the high temperature melting stage of the texturing process. Spherical or thin needle-shaped Y211 grains can be obtained and their size controlled. Microstructural correaltions have shown that the nucleation and growth mechanisms of Y211 grains determine the further YBa 2Cu 3O 7−δ (Y123) formation. Thus, MPMG and SLMG processes appear to be governed by the diffusion of yttrium and also the dissolution mechanism of acicular Y211, while PMP process is mainly controlled by the diffusion of yttrium in the liquid phase to the Y123 growth front. However, the best Bean critical current densities between 0 and 1 T are obtained for the MPMG samples, but with improved processing conditions, the PMP process might be promising.