The bismuth oxycarbonate Bi 2Sr 6−χCu 3O 10(CO 3) 2. : A new 40 K superconductor, second member of the series (Bi 2Sr 2CuO 6) n(Sr 2CuO 2CO 3) n'

Abstract

A new superconductor, Bi 2Sr 6−χCu 3(CO 3) 2O 10, has been isolated for 0⩽χ⩽1. This oxycarbonate exhibits a T c, onset of 40 K, with a Meissner volume fraction of 20%. The powder XRD and the ED study of this phase give evidence for an orthorhombic lattice with the following parameters: a=5.469 (2) A ̊ , b=5.483 (2) A ̊ and c=54.26 (1) A ̊ ; extra reflections, in incommensurate positions along b ∗, are observed corresponding to b'~9×5.5 Å. The HREM investigation shows that the structure of this phase corresponds to the intergrowth of double Sr 2CuO 2CO 3 type layers with single Bi 2Sr 2CuO 6 type layers. Thus, this oxide corresponds to the member “ n=1, n'=2” of the structural series (Bi 2Sr 2CuO 6) n (Sr 2CuO 2CO 3) n' . It is compared to the 30 K superconductor Bi 2Sr 4Cu 2O 8CO 3, first member of the series ( n= n'=1).