The formation mechanism of superconducting Ba2YCu3O7-δ crystals in the melt quenching method and the superconducting properties of the annealed samples were examined. The following results were obtained. Ba2YCu3O7-δ crystals were formed by annealing the melt quenching samples at around 750°C in the air. It was necessary to supply oxygen for the formation of Ba2YCu3O7-δ crystals. The bulk density of the samples annealed at around 900°C was 5.7g/cm3 and the pores which were regarded to be the path of oxygen were observed. The critical temperature Tc, zero of superconducting Ba-Y-Cu-O oxides ranged from 85K to 93K. The critical current density at 77K in the zero magnetic field for the sample annealed at 950°C for 24h in oxygen atmosphere was 35A/cm2.
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Komatsu et al. (1988) studied this question.