Development of REBCO coated conductors. Relationship between microstructure and critical current characteristics

Since the discovery of the YBCO superconductor, many efforts have been made to develop useful superconductive wire and tape for many electrical power applications. Especially, the second generation coated conductors using REBaCuO (RE: rare earth element, Y, Gd, Sm, Nd, Eu etc) compounds have high expectations because of its high critical current density at the liquid nitrogen temperature and under self fields as well as high magnetic fields. Recently, several processes have been successfully developed to introduce effective magnetic flux pinning centers into the REBCO layer in order to enhance the in-field critical current densities. This paper reviews the present status of the research and development about the improvement of critical currents in considerations of nano-scale microstructure. (author)