A comparative study of YBa2Cu4O8 (Y-124) superconductors prepared by a sol-gel method

The aqueous sol-gel synthesis technique for the preparation of YBa2Cu4O8 (Y-124) superconductor was studied using two different complexing agents with the same chemical composition, namely l-(+)-tartaric (natural) and dl-tartaric (synthetic) acids. The characterization of Y-Ba-Cu-O gels by XRD and TGA/DTA measurements showed the individuality of precursor gels and a high level of homogeneity. On the other hand, the morphological features of the gels observed by SEM measurements were slightly different. The ceramic samples calcined for 30 h at 780 °C in a flowing oxygen atmosphere contained homogeneous Y-124 crystallites as a major phase, as was shown by XRD analysis. The TC (onset) observed by resistivity and magnetic susceptibility measurements was approximately the same for the both samples (78-80 K). However, the temperature-resistivity and temperature-magnetic susceptibility dependences were found to be different for the Y-124 samples synthesized by different sol-gel procedures. Such behaviour was discussed in correlation with the morphological properties of the prepared samples.