Oct. 30, 2007 (H10).  In a recent review published in Nature Materials, S.R. Foltyn et al. discuss the materials science challenges for high-Tc superconducting wire.  Thousands of kilometers of high-temperature superconducting wire have now been manufactured for demonstrations of transmission cables, motors, and other electrical power components. The remaining task for materials scientists is to return to the fundamentals and squeeze as much performance as possible from these wonderful and technologically difficult rare-earth (RE) barium cuprate materials, REBa₂Cu₃O_7-δ suitable for use as films on metallic substrates (the coated conductors, CC).  The key to success is understanding and improving flux pinning.  Much success has been achieved in the last 3 years, but there is still a lot of work to do.  Concerted studies of the interrelationships between processing, film defects, and flux pinning are now required, because crossing the threshold of commercial viability may depend upon the kind of performance improvements that can be achieved through a better understanding of these relationships. This article reviews and critically compares the huge amount of recent work on the various methods to improve both self-field critical current density, J_c, and in-field J_c at 65-77K.  It also establishes a methodology for judging the improvement of existing and future efforts in the area.  Figure 1 shows the potentially useful flux pinning defects found in a typical REBa₂Cu₃O_7-δ film or CC.

[1] S. R. Foltyn, L.Civale, J. L. MacManus-Driscoll, Q.X. Jia, B. Maiorov, H. Wang and M. Maley, 
     Nature Materials, 6(9), 631-642 (2007)

Fig. 1 Potentially Useful Flux Pinning Defects Found in a Typical Rare Earth Barium Cuprate Film or Coated Conductor.

(Highlight by J. L. MacManus-Driscoll)