126K superconducting phase in the Ba Ca Cu O system

We have detected a reproducible bulk superconducting transition in the Ba Ca Cu O system at 126 K under ambient pressure. This is the highest transition temperature in a compound system not containing volatile toxic elements such as Tl or Hg. Two other distinct transitions at about 105 and 90 K were also detected. Careful investigation shows that the 126 K superconducting and other phases cannot belong to any of the known layered cuprate compounds. They may belong, instead, to a new compound family with a n n cation ratio of Ba : Ca : Cu 2 :- 1 : . Steps are being taken to improve the granularity and stability of the phases for a definitive structure determination.