Development of Bulk Bi2+xSr3-yCayCu2O8+ ∆ Superconductors by Partial-Melting Route for Fault Current Limiters Application

The production of bulk Bi2+xSr3-yCayCu2O8+ ∆ (Bi-2212) superconductors for fault current limiter application was developed via a partial-melting route. Aiming high I c (critical current), which is the essential superconducting characteristic for application of this material in the construction of Fault Current Limiters (FCL), the produced blocks have predominance of Bi-2212 phase (83 wt%), which characterizes with high values of zero and onset transport critical temperature of 92 K and 97.5 K, respectively. A relatively low transition width, ∆T, from the superconducting to the nor-mal state of 5.5 K, revealed a good intergrain connectivity. Consequently, current measurements on the blocks of Bi-2212 show promising I c values of 230 A and 850 A for direct and alternate current, respectively. It is expected that further increases in the I c values will depend on the elimi-nation of an observed amorphous phase and further reduction of amount and grain sizes of sec-ondary phases, still present in the blocks obtained by the proposed partial-melting route. This may be achieved by a further optimization of the partial-melting processing parameters