The influence of silver and Ag(In) alloy on Y-Ba-Cu-O equilibria around the YBa2Cu3O7-delta superconducting phase

We investigated the effect of silver, Ag(In) alloy and Y2BaCuO5 (the so-cal led Y-211 green phase) on melt-textured samples of YBa2Cu3O7-delta (Y-123) phase in order to check whether better grain growth and alignment were poss ible. 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-T- c superconductors) was not disturbed by addition of silver up to 7.5 wt% wh ile higher concentrations of metal led to a degradation of the texture. Dif ferential thermal analysis and thermogravimetric analysis were used to inve stigate the influence of silver and Ag(In) alloy on the Y-Ba-Cu-O equilibri a around the Y-123 phase. We found a very unexpected thermal behaviour, sim ilar to eutectic equilibrium, when the silver concentration was increased t o 35 wt%. We believe that this effect was essentially due to the increasing ly higher concentration of silver that could react with the impurities pres ent in the melt.