Investigation of the melt-growth process of YbBa2Cu3O7−δ powder in Ag-sheathed tapes

Abstract

We investigated the melt-growth behavior of YbBa₂Cu₃O_7−δ (Yb123) powder under different atmospheres for potential application in Ag-sheathed Yb123 wires. We chose Yb123 because it has the lowest melting temperature of the RE123 (RE = rare earth) phases. Yb123 needs to be melted under low oxygen partial pressure (pO₂) to depress its melt temperature below that of Ag. Here we report that adding Ag powder to Yb123 powder or encasing Yb123 powder in a Ag-sheath further decreases the melting temperature of Yb123. We designed a heat treatment process in which we varied the pO₂ during the heat treatment to melt the Yb123 in a Ag-sheathed powder-in-tube (PIT) wire and then regrow Yb123 on cooling. Based on these studies, we have developed a model for Yb123 melting and growth.