Growth and superconductivity of Bi 2.1Sr 1.9Ca 1.0(Cu 1−yFe y) 2O x single crystal

Abstract

Fe-substituted Bi-2212 single crystals in rods of Bi 2.1Sr 1.9Ca 1.0(Cu 1−yFe y) 2O x with y⩽0.03 have been grown successfully by the floating zone method (FZM). Fe substitution in the rods depresses the growth stability of Bi-2212 crystals and consequently reduces the size of the crystals. The maximum thickness along the c-axis of the single crystals grown from a rod with y=0 is as large as 2 mm, but only 0.4 mm for y=0.03. The maximum Fe solubility limit of the as-grown crystals is less than 0.03 at %. Fe substitution in the crystals decreases sharply not only the superconducting transition temperature, but also the homogeneity of the superconducting phase. The rate of T c decrease with actual Fe-substituted content w in the crystals is as high as 16.7 K/(Fe/(Cu+Fe)) at % for the as-grown crystals of w = 0−0.01, but only 7.3 K/(Fe/(Cu + Fe)) at% for the as-grown crystals of w = 0.01−0.022 and the annealed crystals of w = 0−0.022.