Ba-Ca-Cu-O compositions superconducting at up to 126K and methods for making same

摘要

A material having a superconducting transition temperature (T_c) of 126 K under ambient pressure has been identified. The superconducting material belongs to a Ba—Ca—Cu—O compound family where the cation ratio of Ba:Ca:Cu is 2:2.5+0.5:3.5±0.5. The superconducting material is produced from precursor oxides having nominal formula Ba₂Ca_{n−1+x}Cu_u/yO_x wherein n=3 or 4 and x is 0.4 to 1.0 and y is 0 to 0.8 using high-pressure synthesis. Final synthesis temperature was maintained at less than 950° C. Formation of the superconducting material is sensitive to the state of the precursor oxides, the carbon content of the precursor, and the synthesis temperature, pressure and time.