Effects of grain-domain-size (GDS) on levitation force have been directly investigated and identified in well-textured YBCO bulks. A single-grain-domain YBCO bulk (phi=30mm) was prepared by a top seeded melt growth process, then divided into two, three and four grain-domain to acquire the levitation forces of samples with different GDS. It is found that the levitation force of the samples monotonously decreases with the decreasing of the average GDS (or with the increasing of the total length grain-boundaries of the sample). The maximum levitation force for the single-grain-domain sample is about 1.68, 2.05 and 2.4 times higher than that of the samples with two, three, and four grain-domains. It is concluded that the levitation force of a single-grain-domain YBCO bulk is higher than that of samples with multi-grain-domains. It is also found that the levitation force is proportional to the average grain-domain radius, but inverse proportional to the total length of grain-boundaries of the sample, a simple physical model has been provided and well interpret the experiment results.
