Reaction mechanism of Y-system superconductors in the MPMG method

Abstract
The effect of the melt-quenching step on the refinement of Y2BaCuO5 (211) particles, and phase transformations during crystallization in the MPMG (Melt-Powder-Melt-Growth) process were investigated. The quenched powders, which mainly consisted of Y2O3 and BaCu2O2, were transformed into the 211 and liquid phases by way of the YBa2Cu3Oy (123) phase. The transformation was examined on samples quenched from various temperatures. Through crystallographic examination using several kinds of precursors, it has been demonstrated that the addition of platinum, which is a contaminant from the crucible during the first partial melting step in the MPMG method, can refine the 211 particles.