New oxycarbonate superconductor (Cu0.5C0.5)2Ba3Ca2Cu3O11 (Tc = 91 K) prepared at high pressure

Article abstract of DOI:10.1016/0921-4534(94)00590-7

We prepared a new oxycarbonate superconductor, (Cu_0.5C_0.5)₂Ba₃Ca₂Cu₃O₁₁ at 1250 °C under 5 GPa. This phase is the m = 2 and n = 3 member of a homologous series, (Cu_0.5C_0.5)_mBa_m+1Ca_n-1Cu_nO _2m+2n+1 reported previously. Its X-ray pattern could be indexed assuming a tetragonal subcell with a = 3.852 (1), c = 18.61 (2) angstroms. Electron microscopic observations indicated ordering between Cu and C in the (Cu, C) plane, resulting in a superlattice, a_s = 2a, b_s = b and c_s = 2c with respect to the tetragonal subcell. This new member showed a superconducting transition at 91 K.