NEW HIGH-T(C) SUPERCONDUCTOR FAMILY OF CU-BASED CU1-XBA2CAN-1CUNO2N+4-DELTA WITH T(C)GREATER-THAN-116-K

A new high-temperature and nontoxic superconductor family of Cu1-xBa2Can-1CunO2n+4-delta with critical-temperature (T(c)) > 116 K was discovered. These materials were prepared by the high-pressure technique. A superconductor sample with the highest T(c) contains mainly a Cu1-xBa2Ca3Cu4O12-delta phase. The T(c) value of the Cu1-xBa2Ca3 Cu4O12-delta phase is 116.4 K. The phase has two kinds of tetragonal structures: body-centered tetragonal (bct) and simple tetragonal. The lattice parameters of bct are a = 7.7114 angstrom and c = 35.986 angstrom. The disordering or full occupation of Cu-vacancy sites leads to the simple tetragonal phase with the space group of P4/mmm and the half values of the lattice constants (a = 3.8557 angstrom and c = 17.993 angstrom) of the bct phase. The relationship between the lattice constant c and the number of CuO2 layers n is c/2 = 8.4 + 3.2(n - 1) (angstrom). The small CuO2-block spacing (8.4 angstrom) of this family suggests a lower anisotropy and higher J(c) than in Hg- and Tl-based superconductor families.