Eddy current probing of ceramic superconductors

This paper reports on a simple non- destructive technique that has been developed to measure the homogeneity of conducting materials. The authors determine the resistivity profile of a sample by eddy current probing, and use that as a measure of homogeneity. This technique was used to examine a superconducting YBa2Cu3Ox bulk sample prepared by standard methods. Measurements of the resistivity and Tc (by induction) and x-ray analysis showed no deviation from bulk material previously characterized as homogeneous in the literature. The sample was shown to be inhomogeneous by the eddy current method. The sample was then air quenched successively from 650, 700, and 800 degrees C. Measurements of the quenched material show further inhomogeneity and display the sensitivity and versatility of the technique