BICRYSTAL STUDIES OF HIGH TRANSITION-TEMPERATURE SUPERCONDUCTORS

At the present time, the properties of high angle grain boundaries determine the macroscopic electromagnetic character of all polycrystalline high T-c superconducting cuprates and dictate the types of applications for which these materials can be developed. Understanding and control of their grain boundary properties thus continues to be a key research issue. As was emphasized by Prof. Robert W. Balluffi in his work on internal interfaces, a complete understanding of grain boundary properties requires systematic study of single grain boundaries for which the structure, crystallography, and properties are investigated in a coupled manner. It is precisely these kinds of experiments that have yielded the most insight into the general properties, the range of properties, and structure-property relationships for grain boundaries in the high T-c superconductors. This paper describes the bicrystal studies that have been conducted by our groups at the University of Wisconsin and their key results.