Possibilities of Tc enhancement for already known HTSC compounds

Enhancement of Tc was attempted for RE123 and Bi(Pb)2223 superconductors, because these materials have been well-developed for practical applications, while their Tc's are lower compared to other compounds having similar microstructures, such as Hg1212 and Tl2223, respectively. For the RE123 system, many factors, such as selection of RE element, partial RE substitution for Ba and incorporation of impurities including C, affect Tc mainly through the change of local crystal structure, however, effective methods for large enhancement of Tc were not found. On the other hand, Tc of Bi(Pb)2223 was successfully enhanced up to 116 K by post-annealing at ∼700 deg. C for a long time. Change in cation composition during annealing was suggested to contribute the Tc enhancement of Bi(Pb)2223