Progress report for UDRI/LANL joint research project

Our work has concentrated mainly on exploring the effect of various additives on the bulk superconductive properties of BSCCO 2223 phase. The first phase of our work started by selecting BSCCO precursor powders from several different sources. Lately, our goal is to improve the current carrying capability.of superconducting tapes in the Ag/BSCCO system. The transport current properties of Ag-clad tapes are mainly controlled by the Ag/superconductor interface or the region very close to it. In a rather thick tape, the core region is not considered to be very active in terms of contributing any current to the overall transport J, of the tape. But manufacture of long- length, Ag-sheathed tapes with very thin superconducting cores is very difficult due to the poor strength of these tapes. It is desirable to improve the properties of the entire core so that the overall transport J, of these tapes can be maximized. Our approach was to divide it into two separate aspects. The first part was to understand the nature of interaction between Ag and the BSCCO powder in terms of weak-link quality. The other part was to explore the possibility of engineering the grain boundary characteristics of these polycrystalline ceramic materials with suitable additives through liquid phase sintering. We experimented with various BSCCO powder compositions obtained from several different sources in combination with Ag, zinc oxide, magnesium oxide, tin (IV) oxide, aluminum oxide and antimony (III) oxide. We applied the DTA technique to observe the melting behavior, complex AC susceptibility technique to explore the bulk superconductive properties of various composite samples and XRD technique to identify the detectable phases in these composites. We have also performed some very limited SEM work on few BSCCO/ZnO composite samples