EFFECT OF BASNO3 ADDITIONS IN MPMG-PROCESSED YBCO

Many tentatives have been made these last years to increase the pinnin g properties of melt-textured YBaCuO by secondary phases additions. Th e results are more or less positive depending on the processing condit ions and the reactivity of the dopant, especially its action on the si ze and shape of 211 particles. In this paper, the effect of BaSnO3 add itions up to 30 mol% on the microstructure and the superconducting pro perties of MPMG-processed YBCO is investigated. At high temperatures, BaSnO3 reacts rapidly with the liquid phases to form few microns size inclusions of a stable Y-Ba-Sn-Cu-Pt-O phase. This phase is found to c onsume platinum and to favor 211 coarsening at high temperature. For 3 0% doping, the entire microstructure is strongly affected and for low levels of doping (2% and 5%), we could not evidence any improvement in the superconducting properties, compared to undoped samples. But when the doping level is increased up to 10%, one can locally find a high density of submicron size 211 inclusions and T-c enhancement is observ ed. In this case, we could obtain improved J(c)(B) properties up to 11 0 000 A/cm(2), at 77 K in zero field.