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 Bi2O2 planes is proposed, and the activation energy for Pb2+ diffusion is determined to be 1.47 eV.
The diffusion coefficient of oxygen in the orthorhombic YBa2Cu,0u phase is calculated based on internal friction data. From the calculation, the diffusivity can be expressed as D = = 1.830 x lo-* exp (-1.23 eV/kT) cmZ/s in the temperature range from 400 to 550 "C. The result show that the oxygen diffusion rate in this phase is very slow. K03@@HUHeHT HM@@Y3HH KMcnopoHa B o p~o p o~6~s e c~o t i YBa2Cu,02, @a312 6b1n BbItIEICJIeH Ha OCHOBaHHH BaHHbIX BHYTPeHHerO TpeHkIH. KO3@@HUHeHT AH@@Y3MH MO)KeT 6bITb BbIpaXeH IiaK D = 1,80 X lo-* exp (-1,23 eV/kT) CmZ/8 B TeMIIepaTypHOM MHTepBaJIe 400 EO 550 "c. 3TkI pe3yJIbTaTbI IIOKa3bIBaIOT, 9TO HH$@Y3HH KMCJIOpOHa B 3TOfi @a3e O s e H b MeQJIeHa.
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