SYNTHESIS AND PROPERTIES OF SUPERCONDUCTORS PREPARED FROM ETHYLENEDIAMINETETRAACETIC ACID (EDTA)-ETHYLENEDIAMINE (ED) POLYAMIDE YBC CHELATE

Single-phase Y1Ba2Cu3O7-x has been synthesized by a polymer-metal chel ate precursor technique. Ethylenediaminetetraacetic acid (EDTA)-ethyle nediamine (ED) polyamide was used as chelating polymer for Y, Ba, and Cu. The titration curves of the polymer in the absence and presence of each metal ion showed the chelate formations. The polymer was dissolv ed in water and the metal nitrates of Y, Ba, and Cu (1 : 2 : 3 in mole ratio) were stoichiometrically added to form a homogeneous molecular complex. The clear polymer-metal chelate film was obtained by removal of the solvent without phase separation. This precursor was dried, cal cined, and sintered to develop the superconducting (1,2,3) phase. The 1,2,3 phase produced was found to be pure according to x-ray diffracti on pattern and it possessed good superconducting properties, i.e., the onset of superconductivity was seen at 90.0 K and the resistance rapi dly decreased with decreasing temperature, reaching substantially zero at 88.6 K. Scanning electron microscope (SEM) and face and point anal yses by electron probe microanalysis (EPMA) showed that Y, Ba, and Cu elements were uniformly dispersed at least micron order. (C) 1994 John Wiley & Sons, Inc.