On the correlation of grain boundary misorientation distribution with critical current in bulk processed YBa₂Cu₃O_7-δ

Abstract

The grain boundary misorientation distribution of bulk processed high-T _c superconductor YBa₂Cu₃O_7-δ was studied as a function of processing conditions. The deviation of the grain boundary misorientation distribution (GBMD) from the random distribution, was tested using a χ² analysis, and a grain boundary character distribution (GBCD) based upon the coincidence site lattice (CSL) model was developed and applied. The GBMD and GBCD both showed evolution departing from a random distribution for processing temperatures above 935°C. The GBCD analysis suggests an increase in the population of CSL-related boundaries with annealing time and temperature; and, in particular, the population of boundaries related to CSLs derived from a crystal with c/a > 3 continued to increase with annealing, while the population of boundaries related to other CSLs (c/a = 3) remained essentially constant. Comparison of the GBCD with the volume-averaged J _c for each processing condition, indicates that the increasing proportion of 'c/a > 3' boundaries is related to a reduction in J _c.