The phase relations within the system Tl2O3-BaO-CaO-CuO including Ag has be
en studied with emphasis on the high temperature superconducting phases TlB
a2Ca2Cu3O8.5 (1223 phase), Tl2Ba2Ca2Cu3O10 (2223 phase), TlBa2CaCu2O6.5 (12
12 phase), and Tl2Ba2CaCu2O8 (2212 phase) at 890 degreesC in oxygen atmosph
ere. 1223 has been found to be in equilibrium with a liquid phase which is
Tl poor.