EXTREMELY FINE PRECIPITATES AND FLUX-PINNING IN MELT-PROCESSED YBA2CU3OX

Extremely fine Y2BaCuO5 (21 1) precipitates (approximately 100 angstro m) have been observed by transmission electron microscopy in melt-proc essed YBa2Cu3Ox (123). Magnetization measurements have been performed on samples with and without these ultrafine 211 particles. Our results show that there is a strong correlation between the microstructure an d the flux pinning behavior. The J(c) values have significantly increa sed in a wide range of temperature and field, indicating that these fi ne 211 precipitates can act as strong flux pinning centers in the 123 system.