The field of high temperature superconducting (HTS) power applications is very active in the United States. On the one hand, it is driven by the needs of the electric power grid, which has suffered from declining investment for many years. HTS cables, reactive power devices and fault current limiters address power grid issues. An HTS-based dynamic synchronous condenser is the world's first commercial power product. On the other hand, there is great interest from the US military in applications such as ship propulsion motors, lightweight generators, gyrotron microwave sources and degaussing cables.
We employed Ba-Cu-O substrates for the fabrication of bulk Nd-Ba-Cu-O superconductors using the top-seeded melt-growth method. There were several advantages for the use of Ba-Cu-O substrate compared to conventional substrate materials such as MgO, ZrO2, Al2O3, RE123 and RE211 (RE: rare earth). The Ba-Cu-Odid not react with the precursor and minimized the loss of liquid. Accordingly, the introduction of large-sized cracks was suppressed. We also found that Tc values were high at the bottom regions, which was ascribed to the beneficial effect of Ba-Cu-O in suppressing Nd/Ba substitution. As a result, we could obtain bulk Nd-Ba-Cu-O superconductors that exhibit fairly good field-trapping capabilities even at the bottom surfaces.