Calculation of the diffusion coefficient of Au in Bi-2223 superconductors

Abstract

Undoped Bi-2223 samples were prepared using a conventional solid-state reaction method. Doping of Au in Bi-2223 was carried out by means of diffusion from an evaporated Au film on pellets. We have investigated the effect of Au diffusion and diffusion-annealing duration on the microstructure and superconducting properties of Au-doped samples by performing x-ray diffraction (XRD), scanning electron microscopy (SEM), dc resistivity and critical current density measurements. Gold diffusion in Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy has been studied over the temperature range 500–800 °C using the technique of successive removal of thin layers and the measurements of lattice parameters from XRD patterns at room temperature. The diffusion doping of Bi-2223 by Au causes a significant increase of the lattice parameter c by about 0.19%. This observation is used for calculation of the Au diffusion coefficient in Bi-2223. The Au diffusion coefficient decreases as the diffusion-annealing temperature decreases. The temperature dependence of the Au diffusion coefficient in the range 500–800 °C is described by the relation D = 4.4 × 10−4exp(−1.08 eV/kBT). Au doping of the sample increased the critical transition temperature and the critical current density from 100 ± 0.2 to 104 ± 0.2 K and from 40 to 125 A cm−2, in comparison with those of undoped samples. The critical transition temperature and critical current density of Au-doped samples increased with increasing diffusion-annealing time from 10 to 50 h. Au doping of the sample also improved the surface morphology and increased the high-Tc phase ratio. The possible reasons for the observed improvement in superconducting properties of the samples due to Au diffusion are discussed.

Some physical properties and Vickers hardness measurements of Fe diffusion-doped Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy superconductors

“…Among the metals Au and Ag have been found to be nonpoisoning to YBCO [9], while Ag has been found to be the only metal element that is non-poisoning to the BSCCO system [10]. In our previous works, the role of diffusion annealing time and temperature on the superconducting, structural and mechanical properties of Au diffusion-doped Bi-2223 superconductors were investigated [11][12][13][14][15]. These works indicated that gold doping enhance the superconducting and the mechanical properties of the samples.…”

Effect of zirconium diffusion on the microstructural and superconducting properties of YBa2Cu3O7−δ superconductors

“…It is another interesting result from Fig. 2 that the transition curves of the samples (especially for the pure one) from the normal state to the superconducting state exhibit the double-step behaviour due to the indication of weak links in the inter-granular coupling [26]. Moreover, the onset critical (T onset c ) and offset critical temperatures (T offset c ) inferred from the resistivity graphs are tabulated in Table 1.…”

The effect of Au diffusion on some physical properties of Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy superconductors

“…Superconducting Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy samples were prepared by the standard solid-state reaction method [25,26]. The Au evaporation (thickness of about 50 m) on one face of the samples was carried out.…”

“…To our knowledge, no detailed work has been published on diffusion coefficient of Au in Bi(Pb)-Sr-Ca-Cu-O bulk samples. The only publication on this topic is our recent work on calculation of diffusion coefficient via lattice parameter c in Audiffused samples of Bi-2223 [26].…”