Structure phase transition in FeSr 2YCu 2O 6+δ

Abstract

FeSr 2YCu 2O 6+ δ exhibits superconductivity around 50 K, when it is properly annealed in N 2 atmosphere and subsequently in O 2 atmosphere, although as-synthesized FeSr 2YCu 2O 6+ δ does not exhibit superconductivity. To understand the effect of annealing on superconductivity, we have performed in-situ high-temperature neutron powder diffraction measurements in N 2 atmosphere. We have found that the N 2 annealing at 650 °C promoted the atomic ordering of Cu and Fe and that the phase transition occurred from tetragonal structure to orthorhombic superstructure at 750 °C. The atomic ordering of Cu and Fe did not change at all during the following annealing process. Consequently, this compound exhibits superconductivity by supplying the carrier onto the CuO 2 sheet.