Thermodynamic stability and superconductivity of the Bi–Sr–Ca(Y)–Cu–Li–O system

Abstract

In order to understand the effects of the thermodynamic stability on superconductivity, the thermodynamic stability of the Bi2Sr2CaCu2-xLixOy system and the Bi2Sr2YCu2-xLixOy system was studied. It is found that the broad ranges (0 ≤ x ≤ 0.6) of solid solution may be thermodynamically stable at high temperatures for the Bi2Sr2CaCu2-xLixOy), system and the Bi2Sr2YCu2-xLixOy), system. At equilibrium at low temperatures, however, solid solubility is eliminated, and only the end member compounds and possibly intermediate compounds of fixed composition remain for 0.3 ≤ x ≤ 0.6. It suggests that Li can destroy the thermodynamic stability. Superconductivity is improved by Li-doping, which may be related to the thermodynamic instability.