Optimization of annealing processes on superconductivity of FeSr2YCu2O6+δ

FeSr2YCu2O6+δ (Fe1212) shows superconductivity only after proper annealing in N2 flow, subsequently, annealing in O2 flow and under high O2 pressure. In order to optimize each of the annealing temperature for superconductivity, Fe1212 samples were annealed at various temperature in each annealing process. The optimized annealing condition is annealing in N2 flow at 790 °C, annealing in O2 flow and under high O2 pressure at 270 °C. The resistance began to decrease at 64 K and dropped to zero at 40 K. Superconductivity of Fe1212 was affected by temperature of N2 annealing process rather than that of O2 annealing. The N2 annealing affects the offset superconducting transition temperature rather than the onset superconducting transition temperature. This implies the inter-grain superconductivity in ceramic Fe1212 is affected by N2 annealing temperature.