PHYSICAL AND CHEMICAL CHARACTERIZATIONS OF SILVER-SUBSTITUTED SUPERCONDUCTING PHASE YBA2(CU1-XAGX)3O7-DELTA

Superconducting phases YBa2(Cu1-xAgx)3O7-δ with the nominal compositions x = 0.01 and 0.10 have been prepared by solidstate reaction. Since especially the c unit-cell parameter expands largely with increasing silver content, it is concluded that silver should substitute preferentially at the Cu(1) site in the CuO4 chains. The silver-substituted compounds exhibit Tc of 95 K with a sharp transition in contrast to the Y-Ba-Cu-O system substituted with other cations. Thermal analyses for the reactants mixture indicate that Ag2O loses oxygen at around 400°C and that silver metal evaporates above 900°C. After heat treatment of the sample at 900°C, it was found that Ag content is strongly reduced. After careful analysis the final compositions for the samples with x = 0.01 and x = 0.10 have been determined. © 1990.