Two Superconducting Phases and Their Characteristics in Layered BaTi 2 (Sb 1 −x Bi x ) 2 O with x =0.16
Two correlated superconducting phases are identified in the layered superconductor BaTi2(Sb1-xBix)(2)O (x = 0.16), with the superconducting transition temperatures of T-C = 6K (the high T-C phase) and 3.4K (the low T-C Phase), respectively. The 6K superconducting phase appears first in the as-prepared sample and can decay into the low T-C phase by exposure to an ambient atmosphere for a certain duration. Specially, the high T-C phase can reappear from the decayed sample with the low T-C phase by vacuum annealing. It is also found that the CDW/SDW order occurs only with the 6K superconducting phase. These notable features and alteration of the superconductivity due to the post-processing and external pressure can be explained by the scenario of electronic phase separation.