Lead diffusion and segregation in Pb-Doped Bi-2223 superconductors

Abstract

The isothermal annealing behavior of the Pb‐doped BPSCCO 2223 superconductor in ambient oxygen at various temperatures (650 to 800°C) is studied systematically by in‐situ resistivity measurement, thermogravimetrical analysis (TGA), transmission electron microscope observation (TEM), X‐ray diffraction analysis (XRD), and electron probe micro analysis (EPMA). It is found that upon annealing under oxidizing conditions a Ca2PbO4‐like phase is formed, the sample weight and resistivity increase, and the modulated structure is changed from Pb‐type to Bi‐type gradually. Based on these experimental results, a two‐dimensinal diffusion model of Pb2+ in Bi2O2 planes is proposed, and the activation energy for Pb2+ diffusion is determined to be 1.47 eV.