Microstructure and current limiting factor in Tl and Bi based high Tc superconductor tapes

Microstructure related current limiting factor in Tl-based and Bi-based high temperature superconductor (HTSC) tapes is presented. The Tl-2212 and Tl-1212 superconductor tapes with non-platey grains showed very low critical current density (Jc ∼ 20-50 A/cm2). The low critical current density in the Tl-based superconductor tapes is discussed in terms of the Brick-Wall model. The moderate Jc in Bi-2212 superconductor tapes is discussed in terms of the Railway-Switch model with minor contributions from the Brick-Wall factor. (Author)