Evaluation of inhomogeneities of bulk YBCO superconductors using pulsed field magnetization

Inhomogeneities of a series of bulk melt-grown YBCO superconductors are investigated using the method of the pulsed field magnetization (PFM). Cracking or damages are not found through mapping the trapped field at the maximum pulsed field of 5.1 T in liquid nitrogen (77 K). The amplitude of PFM fields should exceed 1.9 T to guarantee sensibility to inhomogeneity of YBCO bulks. Optimum sensitive pulsed fields are always higher than 1.9 T but they have different amplitudes for different bulk samples. It is found that not only growth sector boundaries (GSB) between the five growth sectors (GS) but also superconducting property variations in these growth sectors contribute to inhomogeneities of bulk YBCO.