Y₂BaCuO₅ Particle Distribution in YBa₂Cu₃O_7-y Grains of Melt Growth Processed YBCO Oxides

Abstract

Y2BaCuO5 (Y211) particle distribution within YBa2Cu3O7-y (Y123) grains of YBCO samples melt growth (MG) processed was examined. To understand the processing variables on the Y211 distribution, a cooling rate (RC=1 K/h to RC=20 K/h) through a peritectic temperature (Tp = 1010 °C), a precursor powder size and composition were changed. Two different Y211 distributions (a linear x-like track and planar butterfly-like pattern) were observed, depending on the processing variables. The linear x-like Y211 tracks were observed in the Y123 samples prepared using a stoichiometric Y123 precursor, whereas the planar butterfly-like Y211 patterns were observed in the Y1.8Ba2.4Cu3.4O7-d (Y1.8) samples prepared using an Y211-excess composition precursor. The track and planar Y211 patterns were clearer at lower RC (slower growth rate of Y123 grains) and for the smaller Y211 particles. In contrast, the random Y211 distribution was dominant at the higher RC and for the larger Y211 particles. The Y211 distribution patterns in the Y123 grains were explained in terms of the interfacial energy difference among growing Y123 fronts.