The Crystal Structures of the Superconducting Oxides Bi₂(Sr_1−<i>x</i>Ca_<i>x</i>)₂CuO_8−δ and Bi₂(Sr_1−<i>y</i>Ca_<i>y</i>)₃Cu₂O_10−δ with 0≤ <i>x</i>≤0.3 and 0.16≤<i>y</i>≤0.33

Abstract

Contrary to reports (see T. Forgan, C. Greaves, Nature 332 (1988) 14), the BiSrCaCu oxide superconductor was not first synthesized in December 1987 in Japan but rather two months earlier in Stuttgart. A patent application was submitted on November 25, 1987. X‐ray and neutron diffraction revealed that the two phases given in the title are present. The positions of the O atoms, which, on the basis of the X‐ray intensities, could only be determined with great difficulty, were found by neutron diffraction. The unique feature of the two structures is that in the (Bi 2 O 4−δ ) part they accommodate all oxidation states of Bi q⊕ for 3&lt;q&lt;5. This might play an important role in the mechanism of superconductivity.