Effect of Lead Content on Bi-2223 Formation by a Two-Powder Process

摘要

Decreasing the total lead content from Pb_(0.4) to Pb_(0.3)significantly stunts Bi-2223 phase development and greatly reduces the critical current density (J_c) of powder-in-tube tapes made by a two-powder process. This effect can be explained on the basis of the solubility limit for lead in 2212. Pb_(0.4) samples exceed the solubility limit for lead in 2212, so lead is rejected to create a lead-rich liquid that enhances the kinetics of 2223 formation during heat treatment. By contrast, a liquid does not form in the Pb_(0.3) sample because its lead content is below the solubility limit. As a result, 2223 formation is much slower and J_c is much lower in the Pb_(0.3) sample.