Effects of precursors with fine BaZrO3 inclusions on the growth and microstructure of textured YBCO

We prepared precursors with fine BaZrO3 inclusions for melt-texture growth of high-temperature superconductors with nominal composition of Y1.5Ba2Cu3O y+x BaZrO3 (x = 0, 0.04, 0.08, and 0.1), by the process of liquid-phase pow der melt-texture growth (LPMG). We then investigated the effects of the pre cursors on the texture growth and the microstructure of composite YBa2Cu3O7 .delta/Y2BaCuO5 (YBCO). The BaZrO3 particles were about 100 nm in size in t he textured YBa2Cu3O7-delta (Y123), observed by the scanning electron micro scopy (SEM). Owing to the pushing effects of growing fronts, fine particles were pushed out of and thus gathered in front of the growing fronts or bet ween Y123 grains. The gathered particles in turn blocked the further growth of the Y123 grains. However, BaZrO3 particles seeded Y123 grains, giving r ise to multigrain growths. These negative effects of BaZrO3 fine particles exclude themselves as effective flux pinning centers in the textured YBCO.