Title :
The effects of stoichiometry in the (Tl,Pb)/sub 1/(Sr,Ba)/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ system on the transport properties of Ag-clad tapes
Author :
Roth, E.P. ; Voigt, J.A. ; Venturini, E.L. ; Halder, Pradipta
Author_Institution :
Sandia Nat. Labs., Albuquerque, NM, USA
fDate :
6/1/1995 12:00:00 AM
Abstract :
Evidence shows that texturing is necessary to achieve high current densities and strong links in the Tl-based superconductors. Conventional sintering is not sufficient to achieve strong links, but instead, melt processing is required to produce platelets which can develop into a textured structure. Changes in the stoichiometry of the precursor powders can lead to enhanced melt-phase formation at lower processing temperatures. An experimental matrix was designed with variations in the Tl/Pb ratio, the total Tl/Pb content, and the Ca/Cu level to change liquid formation and subsequent grain growth. Thirteen compositions were prepared in both pellet form and as Ag-clad tapes to investigate grain development over a range of thermal processing conditions. Tapes were produced using unreacted powders by the powder-in-tube method and processed by conventional furnace annealing. We report here on the transport properties of these tapes, their strong link behavior, and microstructural development.<>
Keywords :
Meissner effect; annealing; barium compounds; calcium compounds; critical current density (superconductivity); crystal microstructure; grain growth; high-temperature superconductors; lead compounds; magnetisation; powder technology; scanning electron microscopy; silver; stoichiometry; strontium compounds; superconducting tapes; superconducting transition temperature; texture; thallium compounds; thermal analysis; (Tl,Pb)/sub 1/(Sr,Ba)/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ system; (TlPb)(SrBa)/sub 2/Ca/sub 2/Cu/sub 3/O-Ag; Ag-clad tapes; Meissner effect; Tl-based superconductors; critical current densities; differential thermal analysis; enhanced melt-phase formation; furnace annealing; grain growth; high temperature superconductors; magnetization; melt processing; microstructural development; pellet form; powder-in-tube method; scanning electron microscopy; stoichiometry; strong links; superconducting transition temperature; texturing; thermal processing conditions; transport properties; Atmosphere; Atmospheric measurements; Gold; High temperature superconductors; Magnetic analysis; Magnetization; Performance evaluation; Powders; Silver; Superconducting films;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
