PROPERTIES OF YBCO OBTAINED BY MODIFIED HYDROXYCARBONATE METHOD

YBCO was synthesized by the co-precipitation of stoichiometric amounts of nitrate solutions of Y, Ba and Cu using a mixture of NaOH, Na2CO3 and H2C2O4 in a molar ratio of 5:1:1 as a precipitation agent. Even af ter prolonged thermal treatment at 950 OC the samples exhibit a zero-r esistance critical temperature of about 87 K. This fact indicates a co pper deficiency of about 0.1, more reduced than in the case of hydroxy carbonate co-precipitation. The as-synthesized samples have a high den sity, reaching 94% of the theoretical density. The SEM analyses show a large grain distribution from microns to tens of microns, favourable for good stacking. (C) 1997 Academic Press Limited.