Abstract
Two joining methods were investigated to develop the low resistivity joint of silver and Y-Ba-Cu-O superconducting oxide (YBCO) with the columnar crystal structure of 123 phase (YBa2Cu3O7-x), which was obtained by unidirectional solidification from liquid+211 (Y2BaCuO5) phases. One method was a solid state processing by the use of hot-press, in which no detectable interaction layer was formed. The interface resistivity (ρc) at 77K measured by the four-prove method decreased with the increase in joining temperature (T) or joining pressure (P), and the minimum value : ρc=2×10-12Ω·m2 was obtained when the joining conditions were P=32MPa, T=873K, t=3600s. The other method was a liquid state processing by using molten silver, in which remarkable interaction layer was formed. Since the reaction was caused by the decomposition of 123 phase to liquid+ 211, the interaction layer was recovered to 123 phase by slow cooling and solidification. This recovering treatment remarkably decreased pp, and the minimum pc value was as low as about 10-12Ω·m2 at 77K, which satisfied the stability criteria for composite conductors.
