Possible flux pinning centers in YBa2Cu3O7-x

Abstract

The critical current density Jc of a superconductor is one of its most important properties for the purposes of applications. Various investigators have made numerous attempts to increase the value of Jc in the high temperature superconductor YBa2Cu3O7-x (Y123) through the introduction of defects into the crystal structure. References 1, 2, and 3 provide a few examples of some of the more recent efforts. In general, defects of an appropriate size should act as flux pinning centers in the material.We have attempted to increase Jc in Y123 samples both through bulk processing techniques and through irradiation by fast neutrons. In an attempt to correlate the microstructures of the materials with the superconducting properties we have studied the materials using TEM. Here, we report on results from two samples. The first is an Y123 sample prepared by the decomposition of YBa2Cu4O8 (Y124). The decomposition process results in Y123 material with a value of Jc which is enhanced by approximately a factor of 10 at low magnetic field at 77 K as compared with Y123 prepared by standard processes. The second sample is one which was irradiated with fast neutrons (> 0.1 MeV) to a fluence of 6.0 x 1017 cm-2. This sample also shows an increase in Jc.