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 Y_1.5Ba₂Cu₃O_y + x BaZrO₃ (x = 0, 0.04, 0.08, and 0.1), by the process of liquid-phase powder melt-texture growth (LPMG). We then investigated the effects of the precursors on the texture growth and the microstructure of composite YBa₂Cu₃O_7-/Y₂BaCuO₅ (YBCO). The BaZrO₃ particles were about 100 nm in size in the textured YBa₂Cu₃O_7- (Y123), observed by the scanning electron microscopy (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 between Y123 grains. The gathered particles in turn blocked the further growth of the Y123 grains. However, BaZrO₃ particles seeded Y123 grains, giving rise to multigrain growths. These negative effects of BaZrO₃ fine particles exclude themselves as effective flux pinning centers in the textured YBCO.