Superconducting YBa2Cu3O7-δ Particles Prepared from Freeze-Dried Nitrates

Abstract
Homogeneous Y-Ba-Cu nitrate powders have been successfully fabricated by a freeze-drying method. Thermal decomposition of them resulted in fine superconducting YBa2Cu3O7-δ powders which were characterized by thermal analysis, SEM observation, X-ray diffraction and dc-magnetization. Results show that a rapid heating of the nitrate powders is required to obtain superconducting material of a good quality without segregation during their transitional liquid phases. In the process used, spherical YBa2Cu3O7-δ with diameters of 20-30 µm can be obtained. These results are compared to results in the case of carbonate.