The influence of silver and Ag(In)alloy on Y-Ba-Cu-O equilibria around the Yb2Cu3O7-δ superconducting phase

We studied the chemical compatibility of Ag, Ag(In) alloy, Y2BaCuO5 (the so-called Y-211 green phase) and YBa2Cu3O7 d (Y-123) phase in order to check if better grain growth and alignment with minimum contamination were possible during the Y-123 melt texturing. We demonstrate that the addition of silver to Y-123 always led to an enhanced texture. The typical microstructure of the composite Y-123 plus Y-211 (that is believed essential for high critical currents in these High Tc superconductors) was not disturbed by addition of silver up to 7.5 wt%, while higher concentrations of metal led to a degradation of the texture. DTA TG analysis was used to investigate the influence of Ag and Ag(In) alloy on the Y Ba Cu O equilibria around the Y-123 phase. We found a very unexpected thermal behaviour, similar to an eutectic equilibrium, when the silver concentration was increased to 35 wt%. We believe that this effect was essentially due to the increasingly higher concentration of silver that could react with the secondary phases present in the melt.