PREPARATION OF FINE YBCO PARTICLES BY DRY- AND WET-TYPE JET MILL

摘要

Superconducting YBCO particles with an average size of 1-2 μm were prepared by dry-type jet mill. It is found from the measurements of critical currents(Ic) that the superconducting transition temperature (Tc) at 91 -92 K is obtained for the YBCO particles which have oriented and elongated grains align parallel to (003) (005) and (006) -plane . On the other hand, fine YBCO particles were prepared from high quality superconducing YBCO powders by wet - type jet mill in a high pressure flow of MEK (methyl-ethyl-ketone: CH _3COCH_2CH_3) or toluene (C_6H_5CH_3) . As a result, the resulting particles are homogenius in MEK. When the mill is operated at a pressure of 127 MPa fine YBCO particles show oriented and polycrystal structures with an average particle size of 164 nm in diameter and with the lattice parameter of 3.9 A in [001]-orientation from TEM(Transmission Electron Microscopy) - studies.They shows superconducting properties with Tc at 91.9K obtained from the experimental magnetization curves as a function of temperatures.