SUPERCRITICAL ANTISOLVENT PRECIPITATION - A NEW TECHNIQUE FOR PREPARING SUBMICRONIC YTTRIUM POWDERS TO IMPROVE YBCO SUPERCONDUCTORS

The solvent, supercritical antisolvent technique (SAS) has been used t o produce submicronic particles of yttrium acetate for the synthesis o f YBCO superconductors. For this purpose, in a continuous SAS apparatu s dimethylsulfoxide (DMSO) as yttrium acetate solvent and supercritica l carbon dioxide as antisolvent have been adopted. Experiments have be en performed in the pressure range between 70 and 160 bar and for temp eratures between 40 and 70 degrees C. Different concentrations of yttr ium acetate in DMSO have also been tested. Various morphologies of ytt rium acetate particles have been obtained, having mean particle diamet ers from 0.1 to 7 mu m. At 40 degrees C and pressures larger than 120 bar, submicronic spherical particles of yttrium acetate of about 0.1 m u m diameter and with a narrow particle size distribution have been ac hieved.