YBCO MPMG samples, with 40% Y2BaCuO5, (Y-211) phase excess, were prepared using different thermal pretreatments during the temperature increase up to the partially melted state. No temperature gradient was applied during the slow-cooling growth process. Presintered samples turned out to be almost single grain, while all the others were characterized by the presence of a higher number of randomly oriented domains. Presintering favours compositional homogeneity, but, most important, enhances YBa2Cu 3O7-x (Y-123) phase solidification kinetics. Though various samples show similar behaviours, concerning the values of magnetization critical-current densities (Jcm) measured at 77 K (Jcm approximately=104 A cm-2 with B//c, B=1 T), levitation forces are subject to noticeable variations related to granular macrostructures and reach a peak of over 2 kg, at 77 K, in the case of presintered material.
ASJC Scopus subject areas