Characterization of the superconducting Bi2Ca3 − sSrsCu2O8 + x (s = 1, 1.5, 2, 2.5) oxides☆

Abstract Four monophasic Bi 2 Ca 3 − s Sr s Cu 2 O 8 + x oxides have been prepared from mixtures of analytical grade Bi 2 O 3 , CaCO 3 , SrCO 3 and CuO, which were ground and heated in air to 1133 K ( s = 1), 1153 K ( s = 1.5 and 2) and 1173 K ( s = 2.5). X-ray powder diffraction showed that the four oxides are isomorphous and orthorhombic, and gave unit cell parameters ( a , b , c and V ) which vary linearly with the strontium content. Resistivity measurements show that the sample for which s = 1 is superconducting, with superconducting order parameter fluctuations in two dimensions.