126 K 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 highes t transition temperature in a compound system not containing volatile toxic elements such as Tl or Hg. Two other distinct transitions at abo ut 105 and 90 K were also detected. Careful investigation shows that t he 126 K superconducting and other phases cannot belong to any of the known layered cuprate compounds. They may belong, instead, to a new co mpound family with a cation ratio of Ba:Ca:Cu = 2: n - 1 : n. Steps ar e being taken to improve the granularity and stability of the phases f or a definitive structure determination.