Refinement mechanism of CeO2 addition on Y2BaCuO5 particles in PMP YBCO bulks

YBCO bulk samples with a nominal composition of YBa2Cu3O6+x+15 wt.% Y2BaCuO5+0.5 wt.% CeO2 have been prepared by the powder melting process technique and the microstructure has been investigated by using scanning electron microscopy and transmission electron microscopy. An obvious refinement effect resulting in Y2BaCuO5 particles with a mean diameter about 500 nm in textured YBCO bulks has been achieved by CeO2 addition. About one-fourth of the Y2BaCuO5 particles were observed to contain at least one nanometric core which was proved to be Y2O3 by selected area diffraction. In addition, a BaCeO3 phase with a square shape was found. Our experimental results provide further evidence for the heterogeneous nucleation mechanism of Y2BaCuO5 particles on Y2O3 previously generated through a reaction between CeO2 and precursors, which was first proposed by Piñol et al. [4] for the melt texture growth process.