Effect of bismuth substitution on liquid formation in thallium-based superconductors

The role of bismuth substitution on the phase development and melting behavior of Tl1.1-xBixBa0.4Sr1.6Ca2Cu3O9-delta was studied. The substitution limit was x = 0.25, and a low-melting liquid was formed when the limit was exceeded. The barium content of the superconductor decreased with increasing bismuth substitution, which coincided with BaBiO3 formation. Magnetization and X-ray diffraction data revealed that the single-layer Tl compound coexists with BaBiO3 up to x = 0.8. For selected compositions, superconductor wire was fabricated by a powder-in-tube process. The critical current density was measured and correlated with the microstructure.